Bit of an ethical dilemma- I sold something a couple of days ago, it already had one bid, then another person also bid on it. The second bidder contacted me the next day to say that a family member had used their account without permission, and requested that I cancel their bid. Since it had already had another bidder, so I knew it would definitely sell, I agreed, and cancelled their bid. Now the original bidder has contacted me (two days after the end of the auction, and only after I'd sent her an invoice for it), to say that she also didn't realise she had bid on the item, won it by mistake, etc, and now can't pay me. She has asked me to offer it to the next bidder (which obviously I can't do, since there isn't one). I suspect that she probably bid on another of the same item when she was outbid on mine, and has now won both of them 
What would you do in this situation? Cancel her bid too, and then re-list the item? Or not?