Talk to her, tell her how much you care and how much of a honor it is to be the one she vents to, tell her she doesn't need this to be happy, that she will be okay, please, assure her that she is loved and that you care for her, if she's okay with that, talk to her about therapy, maybe if she's not okay with that, a hobbie can be therapeutic too! You mentioned swimming, right? Maybe it helps her!