Falling in love with a girl. Need some advice.

Hey, could use some advice.
I'm falling in love with a girl, who so happens to be my manager, but Im like 90% certain that she is into another manager at work. The thing about it is that she also flirts and plays around with me sometimes (not sexually.... just like screwing around w/ each other at work, and are like best friends - she knows I like her). I'm falling in love with the girl, and she's the best thing that has ever happened to me, but I feel that if she left, or he left, she would date him (cant date co-workers). I need some advice as to how I can steer her away from him and towards me. (Hes treats her like crap, but is still attracted to him for some reason)

Thanx in advance