Hi there, I've recently bought some gorgeous shoes (to go with the dress I bought, see "Warning: Prom/Bridal/Ball gowns") and they were listed as a size 8 but they're blatantly not, unfortunately the seller has not replied to my Email so I've relisted them (as the total price but with FREE p+p to help them sell) after I've sold them I'm going to give the seller bad feedback as they did not get back to me at all.
If I were you I'd suggest that, if it's possible for them, to re-sell them, using your original info. Or that you offer to pay (it's only about a £1) to list them for her (?) and that she posts them for whoever wins them (and that you send them the money for the postage, so she's not out of pocket at all).
Unless she wants to have to pay to have them sent back to you and that you re-sell them as a half size smaller, or as a "slim fit"?
I suppose when it comes down to it she's paid for them so if she can't physically use them, for whatever reason, then you both need to come to an arrangement. Unfortunately, the way things are in the UK, shoe/dress sizes are different all over the place, I'm an 8 in most places but every so often I'm a 9, so what can I do?!)
That's what I'd suggest, that way you are at least giving her as many options as possible and she can decide which is best for her.
Good luck