In the first place, a landlord is never obligated to allow a tenant to add additonal people to her lease, other than children and a spouse; any landlord can refuse to do this. In the second place, publically subsidized housing is governed by its own additional, strict rules about household composition, and is not required--and legally cannot, even if they wanted to--tio add additional tenants to a subsidized tenant's lease, not unless those tenants go through the application process, are approved, etc. And publically subsidized housing is generally required to match apartment size to household composition, and to downsize tenants if they have more room than they need. From what  you write, it does not appear that there is anything you can do.