My heart to you and your 14 yo. Disclosing info like that takes such courage! It sounds like you are working hard to support her for having the courage to tell such painful information. Couple of ideas to share that have helped me and mine.....
1- The book "A Terrible Thing Happened" is a children's book that deals with a child having been witness to an unspecified "terrible thing" and how hard it is to walk around and live with that knowledge and memory. It is designed for witnesses to violence and trauma such as sexual abuse. In my home it was VERY useful in opening conversations about how she felt and even better at showing her she was not alone, that the pain and worries were shared, and that she was right to tell. It's under $10 and still available in paperback thru Amazon etc. I've also heard some who liked "Please Tell: A Child's Story about Sexual Abuse" but I haven't actually seen that book.
2- Spend some time teaching and reinforcing the concept of what secrets must be kept and what secrets must NOT be kept. In my family we use a T-N-T test. "Tell or Not Tell" test. It is 3 imple questions that kids ask and depending on the answers know whether they can keep the secret or whether they should stay quiet or whether they must tell. It works for both disclosures and tattling issues. If you want more info, let me know.
Hang in there.... you are not alone!
Upbeat Mom
