My backstabbing ex best friend messaged me?

She's the reason why me and my two year boyfriend broke up, they betrayed me. A few months passed, now she messaged me and was like, "I am still hoping for the day that we could gain back our friendship blah blah" What should I say to her? I would like to answer in a decent manner and let her know that the day she's talking about is never gonna come because of "Obvious" reasons.