The bag is probably authentic, BUT the seller is not one I'd recommend. There are several posts about the seller and her questionable actions as both a buyer and a reseller.
She purchases Coach bags for resale, files snad against the sellers requesting partial refunds, gets the refunds and resells the supposedly damaged bags, thus increasing her profits.
Sellers who don't give in to her partial refund demands get negative feedback from her.
I read the threads over on Ebay involving this seller and I wouldn't go near her stuff with a 10 ft pole, her actions imho are horrible and I can't believe Ebay is allowing this to go on.