I don't know what area of law this falls under... I lent a 'friend' money for a plane ticket. Things have since soured, and the original agreement was oral (in california, where I believe oral agreements are legally binding). The only proof I have of this agreement to repay me is in email form. She says in the email that she would like to repay me. Some time later, I tried to contact her again, and her reply was that she did not owe me the debt and she followed up with the threat of blackmail and also the threat of a lawyer. I would like to collect on this debt, but I am unsure how to proceed (which kind of lawyer to contact, and if I can get a lawyer to take his commission out of the debt collected). The original amount is also lost to me (no receipt), but it is to the tune of 900$, as it is a round trip to europe, and I have indirect paper proof of this fact (an itinerary with my name as payer and her name as passenger).