Buyer claiming wrong size.

I sold a skirt, it was a large, I listed it as a large. I also included measurements, I measured the waistband twice and got 15” across. Buyer got the skirt and immediately raised an issue, claiming the skirt wasn’t listed as the right size, then put it was 16” not 15”. I know it isn’t because I measured when I tried to trade it in the brand specific group for the skirt and when I created the Depop listing. I gave her the option to return for a refund. This was 4 days ago and haven’t heard anything, she hasn’t shipped it back. She never reached out, just raised an issue with Depop.

What do I do? I know Depop tends to side with the buyer, but I don’t want to be out $100 and the skirt. I’m not really a seller, I just resell things that don’t quite work out for me. I’ve never had an issue like this.