Before I come across as a snob - we are all charity shop fans in this house and I have no problem buying second hand.
So Facebook keep notifying me when my MIL comments on posts, and recently it's been a lot of posts for toys on local Buy And Sell pages, always for toys for the kids Christmas. These things are either second hand or on pages dropshipping from China (Wish etc). I don't have a problem with second hand, however the things she buys are questionable. Last year she did the same and the toys were either broken, well worn, had bits missing or just filthy. She doesn't look at anything before she buys either as she gets someone else to pick up.
It's not that she doesn't have money, as she gets vouchers and has spent (estimated) around £600-1000 on these. We have hardly enough space as it is, and half the time all she's causing is hassle for me to take the broken stuff to the dump, which is an 18 mile round trip.
So AIBU to ask her to stop buying from Facebook?