I agree more information is necessary, and it will be difficult for everyone involved. However, if your bf did indeed sexually assault you daughter when she was a kid, there is no reason to believe he wouldn't do it again with another child. IMO the relationship would be over, no matter how hard it would be for me to leave.

As for the comment from a poster that your daughter revealed this information in an immature manner...I think that's a bit judgmental. Telling your mother that her bf assaulted you when you were a kid is extremely stressful, and as she may be suffering from ptsd due to this experience, it is wholly understandable if the presents as a child when confronting an adult who, in her opinion, should have known what was going on.

I'm sorry you're going thru this, and I wish you and your daughter a speedy resolution, and recovery from this trauma.

Take care