My ex-girlfriend ditched me 2 weeks ago for her ex-boyfriend ... now a few days ago her best friend messaged me to say how sorry she was for what my ex done to me, and telling me to be strong ... now were talking everyday, she wants to be my friend on facebook ... i dont know if i stop talk to her bcuz she is my ex-gf bestfriend.

ps: i already forget my ex ...

I think you should really just "unfriend" her.

If you really are over her, then keep her out of your life. She is not to be trusted.