For those wondering about the joke, OP shared it (and it was removed by the mods). The "dark joke" started with the father and stepmother (OP) mocking the daughter's friends for cutting. After harassing the daughter about it, she took off her shirt to prove there were no cuts on her arms. The father then told her to take her undershirt and bra off. The daughter apparently made accusations, something about dreams she kept having. The obvious implication was that the daughter was recalling her father inappropriately doing...Who knows what. OP insists it was just a joke too dark for people to get, and just keeps calling the daughter a liar and a bunch of other things.