How can she at this point? Especially since she claims she has already resold it and the new buyer says it's a fake? Let the new buyer deal with it, and it's her responsibility as the new, current seller.
I think your e-mail to her was perfect. Hopefully she will take your advice and have it authenticated here at tPF.
Jacy, unless you've written your name in big letters all over the bag, she can't proove it's actually yours she selling. She left you good feedback and that should be the end of it. Charge backs aren't that easy, cc companies don't just refund your money because you've changed your mind. Silly buyer, don't worry and enjoy your new bags hon