Can A Landlord Deny Me, The Request To Move To Another Apartment In The Complex Due To Problems With Downstairs Tenant Before Lease Is Up?

My niece rents an apartment in New Jersey. She moved in December 1, 2007. The man downstairs has complained and threatened her, says she makes too much noise and she doesn't. She lives by herself and is hardly ever home. But he complains and it isn't even 10:00pm. The police have been there and she has filed complaints. She asked the landlord if she could move to another apartment and he told her she had to wait until end of lease. In the meantime she lives there in fear. What can be done, anything?