I've had a couple of buyers that seemed a little bit suspect when it came to lost mail, I had a few also claim the replacement never arrived and demanded I send the item a third time. Their feedback usually indicates frequent lost parcels.

So now I just issue immediate refunds if it is a low cost item sent without tracking or proof of postage. I refuse to send out replacements anymore. If I was to cop a neutral or a neg, I'd follow up with "A prompt refund was issued. Can't be held accountable for lost post." Or something similar and try to be as tactful as possible. And either way I'm out of pocket would rather less hassle to go with it.

Good luck getting eBay to remove the feedback. It doesn't really seem to break any policies though, so hopefully eBay will take into account others reporting her and her history.