, I can understand how vexing it is when a buyer makes a complaint and it seems as though it's for no adequate reason.
Just having a look at your completed listings - is the listing of the bamboo nappies x 6 the sale in question?
From what I have gleaned from others (as I'm not a seller), selling used clothes is fraught with difficulties. To avoid problems, it's always best to describe every detail that is relevant to the items. For instance, you didn't mention in the listing that the nappies had been purchased in two batches, and that one batch was thicker than the other.
You also used the words "excellent condition", which can (from what I understand) be a door to a buyer's complaining about the items, as the expectations are then incredibly high. If something is described as "excellent", the buyer may well expect "perfect". If something is described as "very good", the buyer may expect "excellent". The good Lord alone knows what a buyer would expect from a listing stating "unutterably perfect condition" - possibly gold-encrusted nappies made from the feathers of angels' wings.
Some sellers will state condition just slightly below what they really believe the condition to be, for the reasons stated. The buyer then gets a lovely surprise when their purchase turns out to be better than expected. That's something to consider for the future, as well as being very thorough in describing any possible issue. Something like "I noticed when I purchased the second lot of nappies that they weren't quite as thick as the first lot. This is simply the nature of the product, and does not affect the quality. I mention it merely in the interests of thoroughness. There is some piling on the inserts (see photograph [no.] for close-up), which occurred after the first wash (this will always happen, even using the CCDU method which I always used). Velcro and snaps are all fine (see photograph [no.] for close-up)." ... etc.
However, none of that helps you in your current dilemma.
You could, of course, issue a partial refund. I am assuming that your buyer has not opened a case at this point. What sort of refund is she requesting? Is it reasonable? Perhaps - to make a cold hard decision based purely on the best financial outcome for you - reckon up what it would cost you to have the nappies returned to you - that is, the sum of the buyer's postage to you, the postage cost from you to your buyer after the sale, the PayPal fees for the sale, the eBay final value fees for the sale (you should be able to get those credited back, though, if you accept a return), plus whatever cost will be involved in your re-listing or advertising elsewhere.
There's also the aggravation and time factor in re-listing. Also, you need to consider for how much the nappies will sell if you re-list or advertise elsewhere. (I'd use a spreadsheet and various formulae to show me how each scenario works out - partial refund, return, relist, etc.)
Against those things, does the partial refund amount end up sounding like an unpleasant, unfair, but pragmatic outcome?
Or is the partial refund amount requested outrageous?
Honestly, the best decision you can make is when you take emotion out of it, and concentrate on what's best for you with regards to this particular transaction - financially, timewise, etc. But don't let the fear of negative feedback influence your decision (at least, that would be my own stance; it's easy for me to say as I'm a buyer, not a seller). If this is a bad buyer being ridiculously demanding and the requested refund is simply ridiculous, you may want to cut your losses in a nice cheerful way by responding to her with something along these lines:
Dear [buyer]
I'm so sorry you're not happy with these excellent quality nappies. Unfortunately I cannot offer you a partial refund, but am happy for you to return these to me for a full refund, including the postage cost to return these to me via a fully tracked postage method. I want my buyers to be completely happy with their purchases, and as this aappears not to be the case for your purchase, please feel free to return these in the same condition as when they were sent to you.
Best regards,
[name]
Other eBay members will probably have advice for you out of their own experience. I believe some sellers will issue partial refunds as they do not want the negative feedback or the hassle; some will simply accept returns and give full refunds; some sellers will opt to fight it out. I think the fighting it out option is one to avoid if you possibly can (in most circumstances), as it seems almost impossible for a seller to win against a buyer claiming the item's not as described. I know from my relatively short time on the boards here that there are some highly experienced sellers of second-hand clothing who post here with excellent advice.
