I have tried to sell my car to an attorney, she was to make payments and has only made one and none others. what can I do?

a few months ago, I listed my BMW for sale. An attorney and her husband agreed to buy it. They did not have the money to pay for it and I agreed to large sums and to be paid in full by the 13th of March. It has been three months and she has made one payment and the deposit totaling 5k. Four of the thousand, was made to me and the car lender. I deposited it and it caused some problems at my bank. I told the buyer and I believe she is using it against me. Refusing to make payments. I even told her several times over email that I wanted payments made to me and me alone and she told me no, that she did not agree to that and I was in breach of contract. Now I'm behind on the car and no money