Our landlord is trying to lock our attic. Can she do this?

Location: Syracuse, NY

Hello! My 4 roommates and I live in a house that we rent from a well-known rental company. Instead of using the master bedroom, which has a bathroom, we use the finished attic as the 5th bedroom, and the master as a communal room. We did this after thoroughly reviewing the lease which does not say the attic cannot be used as a bedroom. The only mentions of the word "attic" are

1. Furniture Rental: If apartment comes furnished furniture must be left in the residence and not removed. Furniture provided by Landlord cannot be brought outside or used on porches. There is no storage of unwanted furniture by Landlord or in basements or attics.
2. Basements and attics are not for partying.

We have lived in this house with all five roommates for over a month now, with the attic having been furnished by us in June when the lease started. The landlord came over today (having notified us first) checked out the attic, and wrote us an email that she will be locking it on October 9 and to have everything up there moved out by then. She has never verbally said that someone cannot live in the attic, only that we cannot have a sixth roommate.

also - in her email she says "The attic is not to be used as living space as I previously mentioned this during the house tour last Fall." Only 3 of the 5 roommates were on this tour, and she has never mentioned that otherwise. Is that a valid verbal contract?

Under the city''s website, it says the property is not currently a rental property, would this be a code violation on her end? Are my roommates and I really the perpetrators here?

Let me know your thoughts... I don't know if "breach of contract" is the right term but definitely seems violated here...

Author: cholula_sauce