You say both that your husband agreed to extend the lease and that he did not. It has to be one or the other.
If it were me I would sue the woman for return of the security deposit in small claims court and let the judge sort out who owes what. But I understand that's intimidating, with her being a nutty lawyer and all.
As I said in your other thread, you and your husband are both students so you may have a "student legal services" organization available to advise or assist you. Check with your school.

