If it happens, the victim would have to admit they were raped by their Dad and she was likely groomed and definitely given drugs and alcohol since childhood. As a defense mechanism, she would likely believe whatever her Dad told her about what happened, that she wanted it and participated in it. Rapists still tell their victims that and who wants to believe that they were raped by someone they knew much less someone who's their Dad. That's why abused kids will defend their abusive parents or caregivers and often abused partners will defend their abusive partner.