New to This - Buyer Requesting refund

Hi ,



I joined ebay a few weeks ago and have had around 30 sucessful transations- starting to get my head around it all .



i recieved an email today about a dress purchased 2 weeks ago or there abouts ,  - Buyer claims there is a food Stain on the item which as discribed as new .



Brought by my well meaning husband - Far to small the kind you keep for a while and sell when he's not looking or has fortgotten about .



Due to the nature of the item i made various efforts when packaging for post to not crumble the fabric to avoid the seller needing to dryclean / Press before wear . and thought i would have then noticed any marks despite taking numerous photos when first listing .



she describes it as a small mark which to me - you could clean off with not to much effort - and i have my doubts as to weather it was there in the first place .



where do i go from here?  - my listing Claims NO Returns . and she paid under $20 inc post for a $100 item .



Do i ask her to return it ? or do i need to refund first i feel a little like im being taken advantage of .