Service by First Class mail, or even certified mail may be sufficient for service in NJ.
In any event, the OP indicated that the victim intended to ignore the subpoena that she HAS been served with (apparently by mail somehow) and then deny receiving it. In other words, the OP has indicated that his aunt will commit perjury to protect her abuser. Though not an uncommon occurrence, it is possible that the prosecutor and the court will be prepared for this event and either continue the matter or send someone to pick her up (something I have been ordered to do a few times in my career).