How to respond to a manipulative ex who left and is trying to get in touch to make her self feel better?

I'm in love with her. She made so many promises and betrayed me and all these promises, and started seeing someone behind my back and when I found out, she seemed half pleased that I mentioned leaving, and said it's a good idea.

And now she just wants to keep chatting to end things in a healthy and mature way. But it didn't end in a healthy mature, she fucked me over.

I don't know how to balance between not getting angry and not showing weakness and not giving her what she wants.