Wow. Women's shoes in size 15 must be pretty hard to find. I wear a women's 10 1/2 and half sizes are often scarce in the larger sizes. I've had good luck with Zappo's and Macy's, though. One think I like about those is that they offer free return postage, which for online shoe buying is a very good idea.
I just checked XYD's Amazon store and their own website. Their site is a cheap looking little thing with very little stock showing. They seem to be mainly operating through Amazon. My guess is that this is a drop shipper using one of the big asian importers with US warehouses. This is not to berate them in any way, but even if the shoe quality is good, I wouldn't expect much in the customer service department from them.