Lots of 17 year old girls have boyfriend issues. You have no business psycho-analysing your husband's daughter and projecting on to her what you think is her problem. She does not have to have therapy just to satisfy you.

It's sad that your husband lost his relationship with his parents. There is not much you can do about that. It sounds like you greatly resent his ex-wife and want to find her a bad influence. Where does this daughter live . . . with you, or with her mother?