Hi qualifiedpanda,
I'm glad you want to be there for your girlfriend, but questioning her sexual orientation is not a good way to do that. Yes, being a survivor of sexual abuse can give people a lot of complicated feelings around sex, but it does not make someone asexual. If you're going to be there for her, then it doesn't really seem authentic if your support around those experiences is motivated by hoping she'll change her mind about sex - does that make sense?
Has your girlfriend specified what being ace means to her? Some ace people occasionally have sex, some don't but that varies person to person and the only way you can find out what it means to your girlfriend is by speaking to her. Maybe you could read this first, so you've got a bit more of an idea of what being asexual is all about:
Just the Basics, Ace: An Asexuality Primer
Of course, if you know you want to have sex some day, and your girlfriend definitely doesn't then you get to decide if or how long you want to stay in the relationship for. We can talk that through if you ever need to, but it sounds like you're not wanting to have sex real soon?