The crux of this theory is that Alviarin has been marked by the DO to be a Forsaken.

first the "mark" scene:

TITLE: Crossroads of Twilight

CHAPTER: 21 - A Mark

"She's been very useful," Mesaana said, not sounding afraid at all, in a voice that tugged the edge of recognition, "and now I will have to kill her."

"She can be useful," the Myrddraal rasped. "I would not want the Black Ajah destroyed."

"Who are you to challenge one of the Chosen?" Mesaana demanded contemptuously, then ruined the effect by licking her lips.

"Do you think Hand of the Shadow is just a name?" The Myrddraal's voice no longer grated. Hollow, it seemed to boom down caverns from some unimaginable distance. The creature grew as it spoke, swelling in size till its head brushed the ceiling, over two spans up. "You were summoned, and you did not come. My hand reaches far, Mesaana."

Shaking visibly, the Chosen opened her mouth, perhaps to plead, but suddenly black fire flashed around her, and she screamed as her clothing fell away in dust. Bands of black flame bound her arms to her sides, wrapped tight around her legs, and a seething ball of black appeared in her mouth, forcing her jaws wide. She writhed there, standing naked and helpless, and the look in her rolling eyes made Alviarin want to soil herself.

"Do you want to know why one of the Chosen must be punished?" The voice was a bone-grating rasp once more, the Myrddraal seemingly only a too-tall Lurk, but Alviarin was not fooled. "Do you want to watch?" it asked.

She should go facedown on the floor, grovel for her life, but she could not move. She could not look away from that eyeless stare. "No, Great Lord," she managed with a mouth as dry as dust. She knew. It could not be, but she knew. Tears were rolling down her cheeks, she realized.

The Myrddraal smiled again. "Many have fallen from great heights for wanting to know too much."

It flowed toward her - no; not it - the Great Lord, clothed in the skin of a Myrddraal, flowed toward her. He walked on legs, yet there was no other description for the way he moved. The pale, black-clad shape bent toward her, and she would have shrieked when he touched a finger to her forehead. She would have shrieked if she could have summoned any sound at all. Her lungs were airless sacks. The touch burned like red-hot iron. Vaguely, she wondered why she did not smell her own flesh burning. The Great Lord straightened, and the searing pain dwindled, vanished. Her terror did not lessen in the slightest, though.

"You are marked as mine," the Great Lord rasped. "Mesaana will not harm you, now. Unless I give her permission. You will find who threatens my creatures here and deliver them to me." He turned away from her, and the dark armor fell from his body. She was startled when it hit the carpeted floor tiles with a crash of steel rather than simply vanishing. He was clothed in black, and she could not have said whether it was silk or leather or something else. The darkness of it seemed to drink the light from the room. Mesaana began to thrash in her bonds, keening shrilly past the gag in her mouth. "Go now," he said, "if you wish to live another hour." The sound coming from Mesaana rose to a despairing scream."

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okay, so that's alvy being marked. now here is something RJ said about the "mark" that the Chosen recieve:

Question:

How were the Gholams made? Were they created or bred like the Trollocs? How exactly are they controlled if they are immune to the One Power?

Robert Jordan Answers:

The gholam—singular and plural are the same—were created, not bred. Supposedly their creation involved making them so that they would be obedient to the Chosen, whoever they might be at any given time. This was an attempt at copying something that had turned up in Myrddraal, which seem incapable of disobeying one of the Chosen, possibly because of the use of the True Power in creation of the Trollocs, the parent stock of the Myrddraal. Even Aginor, who created the Trollocs, and thus indirectly the Myrddraal, was uncertain about the actual cause. (Becoming one of the Forsaken involves receiving a mark from the Dark One in return for your oaths; this mark is invisible and cannot be sensed by another human being, even another of the Forsaken, but it can be by certain non-human creatures, including Myrddraal and draghkar among others. This may play a part in the Myrddraal's obedience but doesn't explain it completely.) This element in gholam has some flaws, however, as we have seen in a small measure. In any case, if I were you, I wouldn't try giving orders to a gholam unless I were one of the Forsaken.

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of interest here is the forsaken mark. the facts:

1. it is given by the DO in return for your oaths

2.this mark is INVISIBLE and cannot be sensed by other humans, even the Forsaken

3. it can be sensed by myrddraal.

so does the mark given to alviarin fit these 3 things?

the first one is the trickiest to , and whether or not you believe it depends on what you think Shaidar Haran is.

IMO, SH is the Hand of the Shadow, in name as well as nature. it is the way the the DO directly affects events - by moving through SH. Often RJ writes of SH's voice changing to something darker and ominous - i think this is when the DO uses SH as an 'avatar'.

well, when alvy meets SH, we hear him speaking with this DO style voice (not like the rasping myrddraal) just before SH marks miss alvy.

IMO alvy recieved this mark from the DO working through SH.

the next question is if the mark was given in return for alvy's oaths. what follows is my handwavey explanation for why this is so.

i imagine the original forsaken had to pronounce to the GL directly that they would dedicate their lives to Him, since there was no network to recruit darkfriends. then after giving these oaths, they would recieve the mark.

in this day and age however, channelling DFs have already given their oaths to the BA, which is run by alvy and in turn run by forsaken. through these chains of command, IMHO the DO sees these oaths to him as valid... so he can mark whichever BA he pleases, if he so trusts their oaths.

i think the scene above shows SH aka the DO judging Alviarin's loyalty to him and deciding that she is worthy and competent enough to be one of the Chosen (especially considering she's stuffed up less than the existing Chosen).

2nd criteria: that the mark is invisible and undetectable. see what alvy thinks and feels when she leaves her room after being marked:

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"Alviarin did not know how she got out of her rooms - she could not understand how she was upright when her legs felt like water - but she found herself running through the corridors, skirts pulled to her knees and running as hard as she could. Suddenly the head of a wide staircase loomed in front of her, and she barely managed to stop from running right out into the air. Sagging against the wall, shaking, she stared down the curving flight of white marble steps. In her mind, she could see her body breaking as it crashed down the stairway.

Breathing raggedly, in hoarse, raw-throated pants, she put a trembling hand to her forehead. Her thoughts tumbled one over another, as she would have down the stairs. The Great Lord had marked her as his. Her fingers slid across smooth unblemished skin. She had always prized knowledge - power grew from knowledge - but she did not want to know what was happening in the rooms she had left. She wished she did not know that anything was happening. The Great Lord had marked her, but Mesaana would find a way to kill her, for knowing that. The Great Lord had marked her and given her a command. She could live, if she found who was hunting the Black Ajah. Straightening her back with an effort, she hurriedly scrubbed at the tears on her cheeks with the heels of her palms. She could not pull her eyes away from the stairs falling away in front of her. Elaida surely suspected her, but if there was no more to it than that, she could always manufacture a hunt. It just had to include Elaida herself as a threat to be extinguished. Delivered to the Great Lord. Her fingers fluttered to her forehead again. She had the Black Ajah at her command. Smooth, unblemished skin. Talene had been there, in Elaida's rooms. Why had she looked at Yukiri and Doesine that way? Talene was Black, though she did not know that Alviarin was, of course. Would any mark show in a mirror? Was there something that others could see? If she had to manufacture a scheme for Elaida's supposed hunters, Talene might be a place to start. She tried to trace the route any message would have taken from heart to heart before it reached Talene, but she could not stop staring down the stairs, seeing her body bounce and break its way to the bottom. The Great Lord had marked her.

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aha! so the mark left smooth unblemished skin. seems undetectable (unless alvy had some real bad rash on her face and the mark is the only bit that is smooth an unblemished, though this seems unlikely for two reasons - one, RJ has never commented on any existing skin conditions that Alviarin may have, and two, because it's silly).

so the mark is undetectable to the naked eye. This suggests to me that it is a mark of the DO, whether it marks her as Chosen is another matter...

I don't think we can say for certain about the Mark being anything, until we see Alvy interact with shadowspawn. Usually lurks don't think very much of AS, but I predict that next time Alviarin comes across them, it will be commanding them...

I clearly haven't proved conclusively beyond-a-shadow-of-a-doubt etc. that alvy has been marked as Chosen, but IMO it's a good idea for the DO to start replacing the losers (sammael, asmo etc) now before all forsaken are dead. Alvy is a good choice, IMHO – she aint no bumbling fool like Galina or the 13 runaways.

Yay Alviarin, the first new Chosen!