Can my landlord still charge me after the contract ended?

My case is that I had the early determination on my contract (originally is one year but I left in 6 months), so my landlord's agent took my deposit to compensate but after negotiation, she returned 20% to me. But few months later, she found that there were some bills I haven't settled when I left (which I didn't know and she didn't check when I moved out), then now the landlord contact me directly and said I broke the contract and has to charge me back the 20% of the deposit. I just wondering if she can do it. Since i plan to ignore her but she told me that she talked to her solicitor and she will send it to court if I didn't pay. Please help, i am helpless.