Mom wants to resell MOB dress she didn't wear

My mom being my mom bought several dresses for my and my brothers weddings and then usually the week of she would finally decide on one. But, of course, she never returned the others. In her efforts to downsize she wants to sell these dresses online or to consignment shops.

Anyone know a good website that we might be able to sell her dresses through or any experience buying dresses like this on ebay?

Thanks