Can I be charged the difference in rent if I break my lease early

[Robert Cowart]

My LL and I agreed to term our lease early so that my wife and I could buy our own house. We gave her plenty of notice and kept her in the loop as to when we were buying a new home and when we were moving out of the rental. We had 5 months left on the lease(May '17 term) when we moved out, we paid rent for Jan. The LL has found a new tenant that will occupy the house mid Jan. However, she is charging the new tenant $150 less per month. So, the LL is trying to have me pay $150/mo through May to make up the difference. What are my options? She has our security deposit and a prorated amount of our Jan. rent. We are located in Texas.