As someone who had an abusive childhood, multiple SA and a truck load of other issues. I've been on a mental health journey for 10 years via meds and therapy. It is NOT your responsibility to be the one that is there for someone else when they are going through it. Yes, if you choose to fill that role, there are some techniques you can learn to be more supportive. But if you really feel like it's more than you bargained for, that's OK and it doesn't make you an asshole...it makes you honest with yourself about the situation you find yourself in. But be honest with her about what you are capable of, and if you can't do this with her, you would be wise to go ahead and excuse yourself from the relationship.

Before you come at me, I got way more than I bargained for when I married my husband because he masked the entire time we were dating. I chose to stay and help him work through it. Now that it's my turn to do the work, he's there for me. But if he couldn't, I would rather him leave than be there half assed.