She is aroused by me treating her badly but psychologically hates how it makes her feel
Rules and safety are a first.
Expectations are a close second.
Maybe she's feeling guilty about enjoying "roughness" due to her "early experience". Validate the feeling, there's nothing wrong with her, you are not her abuser. Make her feel safe and loved. Even then she might not believe you, so don't take too harshly to it.
My BPDgf/ex who I suspect also was abused used to tell me about wanting "good pain", I told her I would never hurt her and that some "fantasies" were off limits for me, but I could deliver what she needed. It was agreed, no limits crossed, we both enjoyed ourselves.
You need to talk through what is it about that makes her feel bad about it. is it guilt? is it the memories? does she feel unsafe sharing this difficult time in her life with you?
Go easy on her, don't push it. If it comes up, talk it through as she allows it. You know her better, yet still and always take your time to get to know your partner.