After paternaty was proven for my husbands daughter some 7 yrs ago, the little girls last name was changed...

Unless the name change is being used to defraud; or to interfere with any parental rights that your husband has with respect to the child, I can't see any problem here. Your question doesn't make clear issues of placement or custody (custody would affect decision making for the child, and this might fall under the rubric of that sort of decision making). Absent additional facts, it sounds like mom hasn't done anything wrong.

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