Most Helpful Girl
You will have to let go at some point. You are never going to get out of this mess by still having her in your life. Better to do it now then wait for the inevitable. Take a break from her and get perspective on things. You will never find perspective if you still have her around. That is why you are stuck.
Most Helpful Guy
Cut her off and work on yourself. I was in the same exact position as you a year ago. You're her consolation prize if she can't land someone better. It may hurt now, but it's a whole lot better to go through it now, than many times as her "friend".