I used to work with two women, A and B, until we were all made redundant. Still friends with A, who is still friends with B, so I end up asking after B once in a while and hear updates about her. B's dad left when she was tiny and they had no contact growing up. They were recently reunited (B is mid-30s, single, no kids) and felt a mutual attraction that they've acted on. A is scandalised because B confided in her that she is sleeping with her dad. A says the knowledge really upsets her and she wants to tell the police. I think it's not her problem or her business and she should let them act how they wish in private, however shocking incest is. WWYD?