Giving Jahez as in parents giving their daughter things at the of marriage is ok according to Islam. In-laws making ridiculous demands according to their own desires is where you have a problem. In your uncle’s case, if the wife brought the stuff by her own free will and not being pressured into it (by in-laws), there’s nothing wrong with it in principle. As for the family’s issue, if she’s giving them trouble with the furniture in there, then I’d tell her she’s free to take it whenever she wants.