well, first of all, like people said, it sounds like you're the first person she's told about this, and if it took her two years to tell anyone about it, she's obviously going to need a LOT of support. She really needs to report it, but at her own pace, no pressure. Don't do anything like telling authorities or people who would confront her with out her knowing, because that'd probably make her trust you less.
again, like everybody said, lots of support, be slow, be understanding, don't do anything to break fragile trust. i don't have any idea how she's feeling about contact right now, but when i need to feel safe, i think a nice big, warm hug is a good idea. just wrap your arm around her and tell her you're going to help and keep her safe.
i have no idea what i'm talking about, but i hope everything is okay eventually.
Uhm...Large Tuna, have you seen my cell phone device?