Allow her to return, she pays return shipping. If when you get it back it is in good condition, then you can do as you feel best...refund all her money including the new shipping or just refund the item cost. It depends on how YOU want to run your business and give customer service. Some will tell you to refund it all to keep a happy customer and others just refund the item cost. In this case, I would allow a return even though the time has expired.
Consider these questions: Is it truly a poor match or is this buyer's remorse? Did life just get in the way for your buyer and the time limit expired for contacting you? Did you send the buyer swatches first, so its her own darn fault? Lastly, how would you expect to be treated as a buyer in this case?