Women advice im up a creek with no paddle?

Okay I met this girl. Who is super chill and super fun to hang out with. We kind of almost dated. That's a different story in itself. After we decided too just be friends. I thought things would be awkward and what not. I leave for vacation for a week come back and after about a couple weeks we see each other again. It was a little awkward at first but than it was Like it was when we first hang out. Anyway we been hanging out and stuff. I been thinking that she was starting to like me because she been all cute and flirtly with me. A few days ago she started seeing someone....I guess I had more feelings for her than I thought because I found myself a wee bit jealous. She says the day she she stops talking to me is the day one of us is dead. She also told me.our friendship is the best thing that has happened to her in a very long time. I do want to stay her friend cause I do consider her my best friend. But I don't want too be tossed aside if she gets really into this Guy. She kind of already did it. And she had a bad day a little bit ago and called me and was a wreck. Saying things are going bad Bit this Guy and how she is sorry that she leads me on sometimes and that makes her feel like ****. I don't want to be that Guy again but we want to stay friends. Should I cut her off or what