Yeah, Irishbell, I've gotten pretty good over the years about just not arguing and taking whatever and donating, recycling, or trashing what I won't use - my grandmother was a big saver and as she got older it just broke her heart that my aunts and the cleaning lady would come through and throw away all her empty butter tubs and whatnot - so I'd say, sure, Grandma, I'll take them! and take them home and toss them. Ditto a bunch of the stuff my mom gave me when she downsized. For some reason it's just harder with new stuff, and I do get a lot of the "you deserve better!" "this wouldn't make me happy so it must not make you happy!" talk.
The issue I was having - and it was mostly stress, truthfully, I originally posted the week before all three sets of my sons grandparents were about to be here for several days, and each of them are a different special kind of stressor - my partner's mom is always buying me new stuff that I don't want, and then NEVER SHUTTING UP about how weird it is that I didn't want/didn't keep it. I have actually defensively bought appliances to keep her from going out and getting me stuff she's started talking about - because the stuff she does buy is always cheap and not quite what we wanted (like, off-brand Legos that don't stick together, or a plastic spatula when I asked for a metal one.)
I do need to learn to not complain about her so much. While they were here my son learned "tomatos don't go in the fridge!" because I was bitching about it to my partner.