You can refuse the return, but not the refund.
If you really never want to see the shirt again....
If the buyer goes to eBay/Paypal with a dispute, probably Item Not As Described and yes, we know, she will get her refund from PP as soon as she can show she returned the shirt. Then PP will scoop the money from your account, and you will get a black mark for being uncooperative.
Or you can give the money back before she opens the dispute. You don't have to demand the shirt be returned. It's not uncommon for photographs to be exchanged rather than doing expensive returns.
I've found it is not a good idea to discuss how you solve problems before there are problems. Personally, I would drop all the verbiage from About Customer Service to 'greatly appreciated.' Perhaps in favour of saying what the fabric is. You have a 'chiffon' dress for example. Silk chiffon? Rayon chiffon? Polyester chiffon? Washable or dry clean only? Woven or knit? What is the lining? Again, my opinion, but this is more important than whether you take seven day returns. Did you know vegans don't wear silk?