Gabriel.
Stress, seeing her alive again...pick one. And it wasn't just about me, it was about her, too. She's an Orion. It's the best form of comfort someone can offer.
I have no idea. Does it even count as cheating, since she was gone? No one's ever left and come back that quickly before. The only person I've seen make a return is Cordelia and it was months before she returned. The probability she'd be back was... Something I'm not going to estimate out of not wanting to sound like your pointy eared doppelganger.