Yes, she probably means invoice with no postage attached. Send her another, with a note attached pointing out that the postage has been removed.

If she doesn't pay you can still claim your FVF back. After 4 days you can open a dispute and if you hear nothing in another 4 days close it.

Keep all your ebay correspondence and only communicate via the ebay messaging system. If there is complications ebay can look at the communications before making a decision.

Good luck with this one, hopefully it will all work out for you!