Am I a lesbian because I love a girl?

I'm in love with my friend who is also a girl. I fell in love with her in a few months. That was my first love. We used to talk for the whole day and night over the phone and on Facebook. I thought she had the same feelings for me, but I was wrong. I always wanted to touch her warmly and stay with her all my life. But all my dreams get broken apart after she got into a relationship with a guy. I've tried to be in relationship with guys, but I can't be in love with them.