Tried to reason with tenant

Tenancy Deposits

Hi there
My tenant claimed that her husband had left her and that she couldn't afford to live there,her contract ends 16/10/2008 so i arranged to go see her and we both agreed for her to surrender her tenancy once i found a new tenant which i did he was moving in 15th aug,this week i have received a letter from the council saying that i forced her in to signing this letter and after a phone call turned up at the hse few minutes later,she also claims that her son lives with her which is so untrue.Her sister in law was also present who has backed me up on this as she thinks it is not right what she is doing.

She has made me out to be a right bully and the council has told her not to move out on the 15th like they do.They have also stated that if she moves out on the 15th and i move someone in i am in Breach of my Contract.
My Question is if she has signed a letter to say she will move out on the 15th can i still be in breach of my contract.oh and seemingly she is claiming benefits and we know her husband is back with her and he's working and what really annoys me is that they had a big party at there hse at the wkend.