How do I get my security deposit back?

My ex-landlord is withholding my $600 security deposit. On 9/15/14 I notified my landlord that I would be moving out of the unit on 10/15/2014. I lived in the unit for 4 years and 3 months. I advised that I would clean the apartment as best I could and leave the key in the apartment in an agreed upon area. I cleaned the apartment thoroughly and left no damage or garbage behind. The carpeting in the bedroom was moderately soiled and in need of a cleaning, but there were no rips, tears or damages done to it. The hardwood floors in the unit showed some scuff marks, but no damages were left behind. I took great care to leave it as clean as possible after living there for 4 years. The landlord is withholding my entire deposit, citing that she had the carpet ripped out and the hardwood floors re-finished. She also said that she hasn't been able to collect rent on the unit because its not ready to rent. I have not yet received an itemized list of the expenses she is claiming she incur