Depends.
I had it the other way round - a friend gave me a bag of barely worn Monsoon frocks for dd1. I said as I usually do: 'If there's anything we won't use, I'll just drop off at Oxfam, OK?'
Friend:
'Oh don't do that! They'd be worth a few quid on eBay!'
Me: 'Well, look, hadn't you better just put them on eBay then rather than giving them to us?'
Friend: 'Oh I can't be bothered...'
Which translates as Friend: I have spent lots of money I don't have on unnecessary clothes for my dd, & if I eBay them, I shall have to face up to the fact that I have spent eg. £50 on a frock which dd has worn once, & then sold it on for a fiver.
I'm grateful for the clothes, but y'know, when I pass stuff on I do so on the assumption that the recipient will cherry pick through it & then charity shop the rest or pass it on to someone else. But I don't really give it another thought because it's stuff I don't want & have decided isn't worth the faff of selling.
So I suppose YANBU, but I'd probably let it go. Just bypass her next time & take it all straight to the charity shop.