I think you are overthinking and overtalking this sitch.
Go "No Contact" unless it is in regard to your child.
The fact that she cheated on her husband before you guys met isn't good, and I think y'all not being together might be good.
Do you know how you figure this out? Give yourself time and space from her. Spend some time thinking and some time not thinking, just having fun doing GAL stuff. Figure out your issues, but simplify them. Armchair psychology is popular right now but unless you have a professional diagnosing you with something, just think of good and bad behaviors IMO. Keep it Simple.
When she talks, you listen and validate. You keep your opinion to yourself unless she directly asks. And even then, I would think twice about answering her questions about Instagram or what have you been up to. You could respond "I didn't catch it I was busy working on something downstairs." And it would be even better if you were downstairs building something, you know?
H 34 W 29 BD 3/12/18 Divorce Busted Spring 19
It is not things that bother us, but the stories we tell ourselves about things.