Tenant moved out leaving at least $4000 worth of damage. Tenant is demanding I pay security deposit because tenant claim she never received notice of non-payment. Tenant left keys in apartment November 1. Tenant sent instant message to me on December 1. I immediately answered and told tenant that letter was mailed and stated to her again that she is not getting her deposit and that I am going after her for damages. She is contending that I am legally at fault because of she did not receive letter with 30 days. Should I start legal proceedings now or wait until she sues me first. Pictures of damage and certified letter were sent to and tenant signed for both. Can she legally sue me?