There is no place for you to open a case in a situation like this.
I assume that the seller saw your address in the shipping details, and that you sent her an email asking to ship to the other address?
If that is the case, then technically, the seller did exactly as expected by ebay.
You should have adjusted the address before paying so that the seller would have the shipping address on file.
It's very easy for a seller to miss an address change but many will ship to a different address when asked.
Some will refund and then ask that the buyer change the address prior to paying so that the new address shows up on the form the seller gets.
It's also very easy for a buyer to be unaware of the difficulties such a change of address poses for a seller who is trying hard to please.
Cut the seller some slack.