I used to consider myself straight, but lately I've been telling people bisexual because yes, I do believe a straight woman can fall for a lesbian. I had never felt attracted in a romantic way to a woman in my life, though I did find women attractive and enjoyed lesbian porn on occasion. However, the thought of actually being with a women never crossed my mind until few summers ago when I was working in South Carolina and met a wonderful young woman. She was what I guess can be called a stud, an African-American woman who dressed like a man, but she was beautiful and we created a pretty strong connection. After a while, we got along so well and had so much in common that innnocent conversation became flirting and much more before the end of the summer. Until that point I considered myself straight. Now I feel you can't help who you like and that having a relationship with someone of a different sexual orientation is completely possible if the connection is strong enough. Just tell her and if she's open she'll let you know. If not, hopefully she will be understanding enough that you can still continue to be friends. But being honest is the only true way you'll find out.