Why Is She Teasing Me?

Five years ago I started crushing on my friend pretty hard. In the beginning I figured eventually it would go away but over the years I just kept falling into this hopeless emotional abyss which is usually termed as love. Problem was, I had no chance with her and so for five long years, I'd done a pretty kickass job of concealing my feelings for her. About two months ago, through a chain of events I'd rather not go into, we wound up living together...in a one bedroom apartment. On the one hand this temporary situation has made me one happy person, on the other hand it has left me very confused. She recently figured out I had feelings for her and felt bad because for starters she didn't feel the same way. Second, she's currently dating the love of life.
Problem is, ever since we started living together, I can't help but feel she enjoys teasing me. For one she's almost always half naked ( t shirt and underwear only). In bed, she likes to trace her fingers along the lines of
my face every now and then. She's told me a couple times, I'm hot and once she said she's wondered about kissing me before.
I know she's really in love with her girlfriend and she already said she's not into me, so why does she tease me so?
Is she just bored or is there a chance she's attracted to me?