In 2004, I signed a joint lease in New York City with a friend. Both of our names appeared on the lease, and we both paid half of the security.

A year later (2005), after we'd both renewed the lease, she announced that she was moving back home. She gave me two weeks notice and then left. She made a half-hearted attempt to find a replacement roommate, but that person never moved in, and I was left without a roommate for 2 months until I found someone on Craigslist. I paid the rent for two months plus all utilities by myself until the new person moved in.

Because she was breaking the lease, the landlord asked her to sign a statement saying "I relinquish all rights to the apartment, [I]including the security deposit.[I]" She refused to sign that for two years. Finally in 2007, she sent a letter to the landlord and to me stating "I relinquish all rights to the apartment, but [my name inserted here] agrees to pay me half of the security deposit." I did not see this before it came to me, signed by her and notarized, and not only did I NOT agree, I did not sign this form.

Later in 2007, I decided to move. At this point the lease was fully in my name, and the security deposit check was released to me. It was the full amount (including both of our halves and all of the increases which I paid myself) and only my name appeared on the check.

My former roommate is now threatening to sue me for her half of the deposit. Being that she broke the lease and left me without a roommate for 2 months, does she even have a case? And if she does decide to sue, can I countersue for every month her name appeared on the lease when she paid NO money (which comes to over two years worth of rent)?

Any thoughts would be appreciated.

Wait her out. I bet she is just blowing hot air.

You are entitled to reimbursement from her for that amount of time that you were living there without a roommate. That means her share of the rent and utilities for 2 months. Once a roommate replaced her she was no longer responsible.

If her share of the security is greater than that 2 month period then you have to send her the balance. If her share of the security is less than that 2 month period, send her a letter telling her how much she owes you. If she sues you for the security, file a countersuit for the amount that her security did not cover. But remember, it can only cover that time when you didn't have any roommate.

Don't worry about the letter she sent to the landlord. She can't enforce something you didn't sign.