NO NO NO... do not be her friend, not until you are over her. Believe me I KNOW, I was deeply in love with a girl years ago. She didn't want to be with me but loved me as a friend. In my effort to stay in her life I stuck by her in the worst Friend-zone ever. What happened? I kept on loving her for three long years in which I saw her go out with boy after boy, and me? Nothing. Couldn't focus on other girls either and stayed single for that time.
I decided to cut contact finally! After three excrutiating years and decided to move away to another country for uni. At my going away party she finally showed genuine romantic interest in me but it was too late I had made up my mind --HAHA. Maybe after 6 months later I was over her --not completely-- but nothing like before. I was finally free and fell in love again with an even better girl!. but that's a different story.
PS: that same girl has been happily married for 8 months or so, and I felt NOTHING. It's so liberating.
GO NC! Time will do the rest.