Not paying for express post

[print-stuff-and-things]

Hi all, I sold an item earlier this week. The woman asked about it first and I said she must use express post for it to get to her by the weekend. She then buys and pays, without choosing express post. She claimed that there was no express option (which is not correct). I refunded the payment, and asked her to choose express. I got the item ready and took it with me to a hospital appointment (that went all day) and posted it, as she needed it for her wedding (even though I hadn't received the payment), . When I get home, she has purchased another one and hasn't paid for that either... sorry,  this story it just too long and boring to explain! She now has paid for one item again (without express post) and is not responded to cancelling the other one. She also has not communicated with me except to say...'this happened before and the seller just sent it express anyway' Is there anything I can do, or should do? I mean it's not a lot of money, but I think she may have done this before and I went to quite a bit of hassle to get her item to her. Or should I just forget about it! Is there anything that other sellers would do differently in this situation. Thanks