Buyer unhappy with 99p item

[GreenFirefly]

I did add this to the end of a similar thread but thought I should start my own...
I sold some baby clothes for 99p (one item has slight stains as described and photographed). Buyer has sent me a message saying they're rubbish (another item barely used) and has asked for money back - on a 99p item (£3 postage). No case open as yet but I don't want to end up paying for a return when the original postage was 3 times the cost of the item...
Do I not respond and see if she opens a case?
Ask for more information and photos about what she's unhappy with?
Just refund and be glad I've only lost the original postage cost?

IME it is invariably the 99p items that cause the most upset. I've had people pay £15 for an old Boden fleece that had been worn by four dc, and leave glowing feedback, whereas the people who got a nice item for 99p will whinge about the colour or the fit or some other damn thing.

I no longer start items for 99p tbh - there's no incentive to do so now that 99p listings are no longer exempt from listing fees, so just start at a sensible price that will discourage people from bidding jsut for larfs.