It's my belief that a 19 year old daughter has a right to live with her parents. Your husband is one of her parents. So - IMHO - your husband and his daughter have a right to discuss the option of her coming to live there. Given that they've kicked this around in the past, without her moving in, it doesn't sound to me like your husband's daughter is all that seriously interested in actually coming to live at your house.

However, if she did come stay with her dad, it would be appropriate for her to get the help that parents in this country normally provide to teenage children - no more, no less. Nineteen year olds normally do use their parents' TV and Internet. And they normally do eat out of their parent's refrigerater.

Now, Mapper, if the real source of your resentment is that your husband is somewhat of a gigolo, don't blame his daughter for that. Maybe this is a marriage that you need to get out of. You have the option of dumping this guy. He does not have the moral option of dumping his 19 year old daughter.

BTW, if the house you live in is in both your names - yours and your husband's - then, no, the house is not "pretty much" yours . . . . . . and, no, you don't have an automatic veto over him letting his daughter live there, while she is still quite young. But that's kind of a non-issue, since you say SD shows no real interest in moving in. Having her hang around for a few days, now and then, is not really something to get in a lather over. Incidentally, plenty of 19 year olds lack direction and like to be on social media just about every waking moment. I'm not denying that this young woman sounds lazy. (Like father, like daughter.)