How can I get Yahoo to help me stop a client from harassing me on Yahoo Local?

I have a client who has been harassing me on Yahoo Local and other online review sites. Long story short...she was arrested in April 2011 for assaulting one of my employees when her bill came in on the high end of the estimate she was given, and the estimate she agreed to, before work began. She refused to pay the bill. We called the police and although the police could do nothing over her refusal to pay the bill, they did arrest her for assault. Her court case was 2 weeks ago and she was ordered to pay us and to have no contact with our employee. Ever since April she has been on an online campaign to ruin my company's reputation by posting false reviews about my company. I have tried contacting Yahoo Local through the "report abuse" links to no avail. What else can I do to make this stop? Why won't Yahoo assist me with this? They ignore all my emails and I cannot find a phone number to call them. The police tell me there is nothing they can do about the online harassment even though I can prove it's her.