It is NOT your fault!! We all have a past and things we wish we didn't do. That's okay, that's life!! That's learning and growing!! You are not that person anymore, you have grown, matured and moved on. IMO, it's not healthy to be with someone who lives in the past and continues to throw it in your face. I can guarantee she has things in her past that she isn't proud of either and wouldn't want to re-live it over and over and be judged by it.

I personally couldn't be with a person like this and would be looking at leaving if things haven't gotten better in 4 years. Life is too short and you're too young to settle for that kind of love. Every relationship has it's own issues but this goes far beyond that IMO. If it was a male partner abusing you, people would be 100% telling you to leave and find protection. The fact that your partner is female should not matter. Abuse is abuse.

Good luck! Please seek professional help