mary mccellan will not pay for new a/c unit Internet

I installed a new Trane hvac unit in a house that she rents back in dec,2011 and can not get paid. I have been tring to take her to court but she has made it hard on the sheriff to find her. When I did the job she told me that the house owner could not pay until jan,6th 2012. I said ok the date came and went with no payment.She told me that the owners loan did not go thought. What loan? When she told me that they where in the military and could not be found. One new lie after the other. When I checked with the city I found out that her family owned the house. She told me that her company name was mary mc LLc.in suffolk. When you go to that adress they tell you that she now lives in NC. She never calls back , and tries to say that the unit did not work in a/c and had to call someone to fix. Why didn't she call me? because she had not paid a penny for the unit that heated her house all winter. I found this sight when I was tring to hunt her down for court. I do my company the old way with a hand shake. I do  few contracts and its worked great for many years for jobs from $100 to 30.000 and this is the first time I have been riped off. I usually can tell a lot about a person when I meet them and if I don't like you I do not do work for you.   I thought Mary was a very nice person but I guess I was wrong and now I have to change the way I work. I have other real eastate customers that are great and pay very fast so that there renters are happy. Mary is not one of them. Willie