She's as mixed up as he is.

I assume she's looking for an apartment for her and her fiance at the beginning. A strange man is in the apartment and she has sex with him. Later, she keeps going back to the apartment to be intimate with him.
But she can't seem to make up her mind about loving him. When he finally reveals who he really is and seems happy, she says it's over.
Isn't she as unstable as he? Because she kills him.