Explain to her what went down without getting ghetto.
Plus: you get to tell your side of the story.
Minus: you have to re-live the story, rather than moving on like you already did.
2. Find a graceful way to bow out.
Plus: plausible deniability.
Minus: no one will know what a classy broad you are.
3. Not respond at all.
Plus: plausible deniability, or getting promoted to permanent flake status.
Minus: you may be furthering any rumors that may have preempted the invite anyway.
4. Show up and live your life out loud.
Plus: you get to be you.
Minus: you have to spend time with the ex.
5. Blog about it to see if someone else has a better idea.
Plus: you give up control to a higher being.
Minus: that higher being may be spam.
It's been a long time at #2, and I'm growing weary of being a grown-up.
So I'm going with #5.