>>92053452She didn't want him fucking his cousin, before Peggy leaves Bill has no idea which of them is. Once Peggy reminds him of this he doesn't want to fuck any of them for a while.
Also, just like his Aunt Esme points out, Bill has no intention of staying in Louisiana, having children, and inheriting and taking care of the property, he's just overwhelmed that three beautiful women all want to fuck him, and likewise the girls really only want him so that they can be the ones to inherit the estate. None of them really have noble intentions, especially the girl who's actually Bill's cousin, and Peggy, taking a good read of the situation for once, is in the right when she says it's a bad idea.