im in love with a bi girl, who has a "girlfriend" what do i do??

There is this girl on met on a college trip. when we met we both felt like we were friends forever, we both get along and love each others company...sound good so far, but she has a "girlfriend", who she does things with. I haven't been able to make any "moves" yet because I like so much that I don't want to lose her. I don't know what her situation is with her "friend". Her "girlfriend" is very jealous of me but likes me because she knows what a good guy I am and how I look out for and treat "Ms.X" like gold. when we are together we both can feel the tension between us, what the hell do I do? what do I say to express myself to her without pushing her away, and should I encourage her to breakup with her "friend"? I NEED HELP PLEASE!!! Tweet