You didn't do anything wrong and there is nothing wrong with you. Most people would be upset to learn that someone they care for has a sex addiction and a history of cheating.

People can overcome that kind of behavior. Perhaps your girlfriend could explain why she believes she is 'over' that now?

And why did she tell you? Was it a warning?

I may be misreading your post, but I consider it a red flag that she is upset that you are 'judging' her. It sounds to me like she has not fully accepted how wrong her behavior has been in the past, which is not a good sign for your future together. Good luck with whatever you decide to do.