Um, correct me if I'm wrong, but I took it as she was going 2 c her man for 1 last fuck. When she goes 2 the door, that's when she is caught off guard by the other woman ( 1)looking a lil shocked/disappointed. 2)Sizing her up, lookin her up and down 3)hesitating 2 walk in). But since she says she knows the relationship won't work and she just wants 2 fuck, then that's when she decides she is joining n on the fun 2 (that's y she pulls her back n by the arm)