Welcome to Psych Central Arialside. It sounds like your girlfriend is resisting facing the inner turmoil. If you could get her to a couple's therapy session, it might come out.
Sharing intimacy is a vulnerable moment of great tenderness. When it is marred by anger, violence and pain, it raises a wall that is not easily lowered. It is a barrier to true intimacy, not just physical closeness.

Personally I would scale back intimacy since it is bringing up unexplainable anger in her.

there are some forums here that you might visit.

Survivors of Abuse - Forums at Psych Central

Post-traumatic Stress - Forums at Psych Central

Keep in mind that some people are triggered emotional by frank discussion of sex. you will get more responses if you describe in future posts less graphic details. Just a tip so you can get better responses.