Well, I KNOW the situation first hand, and I say I would go with my principals. My personal beliefs and self-respect are far more important than some verbal agreement to work on a project. This friend screwed you big-time, and forgiveness is GREAT but not if they don't even apologize or act like they care. You KNOW my opinion of her... What goes around comes around and it would be much easier to sever ties now than down the road. Just my 2 cents...
P.S. NEVER get even or karma will bite ur azz, too
Kisses,
Moe