You committed yourself to your daughter when you adopted her, and you have a duty to ensure that she is not harmed or hurt.
Your family chose to disbelieve the accounts of the abuse that she suffered, and to continue to accept their abuser into their midst. The family are now expecting you to subject your daughter to psychological trauma of being in his presence.
By doing so, you would be sending the message to your daughter that her experience, her fear and her trauma are less important than staying on the right side of your family by being friendly with her abuser.
So your choice is - will you put your daughter first, or will you put her abuser first?
It's your decision.