Hey, Bewildered.
I think you are getting a lot of "don't even bother" messages from people here because that's our experience. I know that any type of "reaction" I have to my exN, whether normal people would find it appropriate or not, is a warped little invitation in his head ("Oh, I got a reaction......me...mee....meee......etc") It doesn't matter what you say.
However, I think sometimes just walking away, or shutting down just isn't proactive enough. You may have to back it up...not with an explanation (they don't get those....think it's engagement....) but with a word or two to shut them down.
NO! Is a really good word. Of course most N types think it means something other than no, so I get why Hoppy would have said, just leave.....but NO!! said in increasingly louder volumes even gets the real jackass to stop (public humiliation and all).
So, she bugs you to dance? "No, thank you.....and if needed, repeat NO NO NO" And then leave...she follows? Loudly, say "stop bothering/harrassing me.." My ex hates that.....but when I hang up the phone, there is not a lot he can do. So you could say, more proactively, exactly WHAT YOU WANT HER TO DO/ NOT DO. Still, make it clear there is no debate.
Forget about retaliatory comments....they shout: "I still care and I sit up nights thinking of what I will say to you".
I could add that you might not want to be in those social situations that she might also be in, for a while. Why? Because unless YOU are completely clear of her energy/what she did to you, no matter what you say or do....the energy is still there. When you get to the point where she could be a gnat to you, someone you don't even think about, really, then seeing her in a club, with a new boyfriend, etc, won't even phase you at all. She could be anyone.