Hi, we listed a mobile food trailer for sale on Gumtree. A person from Qld was interested and offered a price lower than we wanted. She then messaged she would come to look at it and would pay a deposit to show she was serious and not a time waster. On Sunday morning she messaged to ask for our bank details, but when we sent them said she didn't receive them. We then sent her 2 more messages asking if she'd gotten the bank details but she did not respond. Another local SA buyer had said he would come that afternoon to inspect but we weren't sure if he'd turn up. He did turn up that afternoon and offered the full asking price in cash, which we accepted. When we messaged the Qld buyer to say it was sold, she said she had paid a deposit that afternoon and said she had sent us payment notification. We double checked email and texts but had not received any notification she had paid the deposit. She then said she had already booked airfares and accomm to come to Adelaide. We apologised extensively and said if we had been aware she had made a deposit we would have honoured it but did not get that communication from her. We offered to pay some of her expenses as a gesture of goodwill. She became quite nasty and abusive as obviously she was very angry, threatening legal action if we did not "refund" her airfare and accommodation expenses. The next morning her deposit was in our bank account so we immediately refunded it and texted her to notify her of this. We discovered she had booked accomm through booking.com and her booking could be cancelled for free - when we texted her regarding this she replied she had "just found that out" and cancelled it - but I expect she wouldn't have told us that if we hadn't queried it and would have happily let us pay her for it. Now she is still demanding we "refund" her airfares and has been so rude and abusive. As we have refunded her deposit, are we obligated to pay her airfare expenses? Can she make any claim against us for them? Thanks for your help