I went ahead and rewatched the scene (because I was afraid that my partiality for Boomer had biased me) and she definitely avoids getting close to him until he asks her if something's wrong (she ducks away from a kiss and pulls away from him in a clear attempt to leave) -- at that point, she gets this determined look in her eyes and pulls him in for a kiss because it's clear that he's not going to just let her slip away. He's also the one to pull both her shirt and his off and there's a point in the scene where she pushes him away quite forcefully (then he takes his shirt off and we pan to the closet where Athena is). And when he first nuzzles her at the beginning, she has a very hunted look in her eyes in the mirror and there's this tiny intake of breath from her that just killed me this time -- she's definitely startled. She's just good at covering.