A couple of years ago she de-friended me on facebook and forbade me to go to her page.
Wait a minute!!
I wasn't going to reply because everyone is saying the same thing I would say - Red Flag, Deal Breaker for me personally.
But now you're saying that she checks your FB but you two aren't even friends and you're not allowed to see her page? Oh Hell NO!!
Big, Gigantic, Candy-Apple Red Flag!!!
So, the real question is not about whether her expectation of privacy after cheating is reasonable. The real question in my mind is how much more are you willing to take? She's obviously still playing by the Wayward Rules. When do you get to say "Enough is enough. Here is my boundary."
(((lots of hugs)))