We are sorry to hear about your kallah's past suffering.
If the abuse included penetration and took place after age three, she is required to inform her chatan. No one else needs to be informed and the ketubah need not be changed.
If the abuse did not include penetration or occurred only before she was three, she is not required to tell anyone. On the other hand, she is fully permitted to tell her chatan, if she thinks it may help her to do so.
In a sensitive situation such as this, it may be particularly useful to put your kallah in contact with a frum, trained sexual therapist. We hope that what she has been through does not affect intimacy with her chatan, but professional guidance may help her avoid difficulties or cope with them as they arise.
Behatzlacha and please let us know if we can be of further assistance.