Letter from landlord’s attorney saying that I’m violating my lease by subleasing. Pls. give advice?

My fiancee moved in w/me to cut down the expense of our wedding which we intend to stay in the apartment until we find something bigger. I notified the landlord via letter to be placed in my rental file as stated in the month to month lease agreement. Now she is trying to have us evicted because she says that I’m subleasing because my fiancee has been paying the rent from his checking account. Three months ago, I filed a claim against the complex because my vehicle was damaged due to her negligence of not notifying the tenants that the entrance gate was broken. Every since then I have been have problems with her. Oh year, let’s not forget that other tenants have people living with them that are doing the same thing and not having any problems with the landlord! What should I do?