So, an update. I hadn't received it by Wed the 10th, so I sent a message to the seller asking if she was able to get confirmation from her courier that it was shipped and if so, if I could have the tracking number to track it. She responded right away, saying I should have received it by now, and telling me that she had a receipt from the courier, but no tracking numbers. It eventually arrived on the 11th, with postage dated Monday the 8th, so it clearly was not shipped when I was told it would be shipped. When I told the seller what day it had arrived, and that the postage was dated on the 8th, her response was "thanks for letting me know. I'm glad it's there now". I gave her a generally positive feedback, citing how beautiful it is, and the quickness of her response when I gave her something concrete to work with. I did mention a slow response time otherwise.
For those who asked - it was a custom made item. When I asked about a timeframe initially for it to be done, I was asked when I wanted it done. I asked if they could have it ready for an event I was going to in a couple of weeks, and they said they'd try and have it ready. When I messaged them a few days before the event, they said it wouldn't be ready after all. I messaged them about a week later to check on the status, and that's when everything happened. So I never really got a clear timeframe on when I should have expected it to be done.