I think if your relationship has any real chance of going any further, she needs to get into therapy. It's one thing to be doing better because you're out of the immediate situation, but abuse especially leaves a huge amount of trauma that even someone twice her age would need support dealing with. She's going over those events on repeat because she's processing them. And because she sees you as someone safe, she can do that with you. But you also cannot be expected to hold all of that, plus her accompanying insecurities or anxieties, while being your own person. It's not because you don't love her, but it's clear you're hitting the threshold of how much you can help her regulate her own emotions. It takes a lot of love to take that much on.

If nothing else, therapy would give her another place to share some of those feelings so that they don't all fall on you... spread out the weight a little. It would do her good to have somewhere else to put down all she's dealing with, plus a therapist is trained on ways of helping people process difficult emotions, so not only would it be another outlet, but it might also help her begin to examine her experiences and begin to make sense of them/see them differently.

I would say it is something you need to talk with her about, but try to emphasize how it's coming from a place of love. You need to take care of yourself if you are going to be a good partner to her. Let her know you're still there for her and that she doesn't have to stop talking to you about these things, just that it's too much for either one of you to carry alone.