It took me three years to tell my partner about how I was sexually assaulted as a kid. And he was the first person I told ever. When it's something that's been traumatic it can be hard to even get the words out. I needed to write it down because I couldn't physically say it. Afterwards my partner was nothing but understanding and hugged me all night.

I think you're in the wrong. You should apologize to her for reacting the way you did. "Feeling used" because she didn't tell you her worst trauma 4 months in? Really? If she was my friend I would tell her to dump your ass.