This will be based off of my headcanons and theories too, so bear with me, if you will.

You can be anyone in this AU - a toon, a handler, even a twisted; I said anyone.

You and Glisten are pretty close. Best friends, I would say. You lived on the same floor, so you would often hang out with each other. You were, so far, the only one who knew about Glisten's crippling fears of imperfection and abandonment, other than his toon handler, who would probably abuse him for it as he always did.

Of course, the lights were out in Gardenview; the handlers just assumed all the toons were asleep by now. In the room next to you, you hear the loud shattering of a mirror, then sobbing.

You go over to the next room, and see... Glisten, with half his mirror face cracked. His makeup was running, and you could see bruises on random parts of him.

(It's based off of my headcanon that the more upset Glisten is, the more his mirror cracks, and when it fully shatters, he becomes Twisted Glisten and starts begging for you to stay like he would in the game itself.)