Actually, I don't think that was bad at all. You opened with a great version of "this is your mess; you need to clean it up," and you ended it with some strong honesty, truth darts, and overall a very principled stand."
for now, you do NOTHING. If she keeps badgering her, tell her to STOP badgering you, and tell her "this is your mess; you need to clean it up. You know what you need to do." Do NOT delineate it for her, or she will ONLY do those few specific steps you specify.
When she tries to deny an affair, stop her. "STOP IT. We both know you're lying right now, and it's very disrespectful. If you keep lying to me, I'm hanging up (or leaving, or whatever)."
Do 20% of the above, and 80% dark/dim, take 3 advil and call me in the morning.
Puppy
This.
You are doing great. Cheers
M22,H45,W45 S21/18D12 Retain faith that you will prevail in the end, regardless of the difficulties and at the same time confront the most brutal facts of your current reality, whatever they might be.