Much will depend upon what your lease says. There may also be an interpretation that he is "living" there for all intents and purposes. I recommend you take a copy of your lease to a local landlord/tenant attorney for review.
There may be any number of other reasons she would have a legitimate interest based upon safety of tenants, complaints by other tenants or neighbors, parking limitations/enforcement, etc. There just isn't enough information here.
Please note that this response is based upon the limited information available in the question. In addition, it is not intended to create an attorney/client relationship and is offered only as general information and not as legal advice.