My question involves landlord-tenant law in the State of: New york

My roommate and I both have girlfriends. They both stay with us (whole different issue, and yes violation of the lease). His girlfriend was just added to our lease (its up in October) and she isn't to fond of me and my girlfriend. She tells lies to make her sound better, actually turned the hot water off on my girlfriend during a shower so she could use it and is just all around a deceiving person. My landlord said he wouldn't renew for me because my girlfriend "lives" here, and she has a key which isn't allowed. Nothing on the lease about not giving a key to someone. The kicker is my roommates girlfriend has been here just as long. She actually was renting upstairs still while living down here and had a key before my girlfriend ever did. We think she wants to stay and is trying to get us kicked out. Anyway I was never informed of her being added to the lease. Is that allowed? My landlord told me its between me and my roommate to talk about but he claims he didn't know she was added either. Not sure if I trust him though. Please Help! Also..is that some form of discrimination?