My sister was named Executor of my father's Will. She is suing me for mishandling his social security payments and requesting that I give full account of all money I received on behalf of my father. His SS payments used to go directly to my bank account. I never kept records because I did not see this coming from her. I did the best I could with his money and took care of him. How can I defend myself against a law suit like this ?

Where are your bank statements? If the executrix of your father's estate is asking for an accounting, then by law, you have to provide it.