Threadhopping/threadjacking: Go for it! The more the merrier.
Backtagging: Absolutely~
Quirky texts: Not a problem. If Faye can handle Ed, she can handle anything - maybe not happily, but she can.
Romantic relationships: Mmmm. Not likely to happen, not with the whole trust issue thing, and the fact she's not the easiest person to get along with.
Fourth Walling: Sure. She's post series, so why not.
Hugging/kissing: Totally at the character's own risk. It could go well, or they could walk away with a broken nose.
Flirting: Nope. Just kidding. Faye's a champion flirt and likes it when others know how to play the game.
Fighting and injuries: Talk to me first! I'm not against either. I just like to have things planned out beforehand.
Death: No death please.
Private post hacking: Should I ever decide one of Faye's posts will be private and worth hacking, I'll indicate if it can be, or you can always ask me about it.
Mindreading/telepathy: Maybe, baby. It depends on the situation, so we can discuss it.
Did I miss anything? You can ask me here^^