What is a mother to do when she finds out her huband sexually abuse her daughter?

IF, and only if, you are certain that this occurred, then you have only one option, and that is to report this serious crime to your local law enforcement.

Make sure that the allegations are true. If they are, then leave and call the police. Today. Now. Go to a shelter or a hotel.

Tell your daughter that you love her, unconditionally, and that she's a wonderful and beautiful person. She's not At Fault, she's not dirty, and she's been hurt by someone who failed at the one job he had.

Your job is to take up the slack that the husband left. Take care of your daughter because she will require a lot of extra love and care.

Find her a good psychologist; she's going to need it. So will you.

Good luck.

talk to the police they will listen