Hi everybody, I need advice on a matter that my girlfriend and I had recently brought up.

Firstly, that background of the story. Last month for her birthday, I had planned a surprise gathering at a restaurant for her, my parents, and myself. The problem was that I completely disregarded the fact that on a prior night I had asked her to enter my house/my parent's house to get a form. In the end, I was blind to her anxiety over entering the house and practically forced her to go in when I wasn't home. She knew my mom knew about her entering the house, my mom's rule is "If it's someone we know deeply, I don't mind."
Unfortunately, from that point my girlfriend thinks my parents hate her because of a past incident with her ex's parents.
Back to her birthday, the night before her birthday we had a fight over who was and wasn't supposed to be coming to the dinner. She found out about my parents coming and wanted her sister to come along. I wasn't too eager about that and we both got upset. In the end, we went to dinner with each other and had a nice time.

But here we are a month later and recently I asked about her somewhat distant behavior at times. She revealed to me that, while she can usually forget the past, this time she can't move it aside. When she tries to move it aside, she feels her emotions shutting down.

The bottom line is that I downplayed her greatest fear and she has said that if she can't recover from this that we'd break up. I really don't want that and I'd like to move forward with our relationship, not away.

What advice can anyone give me?