Its a generational/cultural thing to a degree. My parents are of a very poor working class background and they wouldn't so much as buy a book from a charity shop because they would never BE in a charity shop, they view many things that are becoming or are normal for younger generations - free-cycle etc as "begging"
I don't agree, but I understand their perspective insofar as I know for them they would feel ashamed to buy or use something second hand excepting MAYBE furniture.
Because they're coming from an experience of their families could pretty much ONLY manage by "accepting charity" a lot of the time. They were clothed in donated and hand me down clothes and it was noticed and they were denigrated and bullied for it from childhood right up until my dad was doing well in the army - which wasn't as soon as he joined as contrary to popular opinion army pay is actually pretty shit until you get a few promotions.
By this point my youngest sibling was in school.
They wanted (as most parents do) to "do better" for their kids.
Your DH is STILL their "kid" and especially with him being so sick at the moment that may well be making your mil feel as if he needs protecting just like when he WAS still a child yet she may feel largely unable to do anything tangible helpful.
She may be hurt that neither you nor Dh asked her/them for this and may even feel she has "failed" him in some way in that as she sees it, he felt unable to bring himself to ask her.
If your dd was an adult, but sick, and needed something as a result of being sick that you could quickly and easily get for her, wouldn't you be hurt if instead of asking you she asked publicly for "charity"?
I know I would be if my dd did that.
We younger generations have a different feeling and perspective on such things, to a point.
It's far more commonplace now to ask for help (there are pros and cons to this) and the movement of consumables between people according to need is of course much better for the environment.
But maybe she just wanted the opportunity to show her son she cares? To have something she could actually DO for him at this difficult time? To feel they have a relationship where he feels comfortable asking his parents?
Just a perspective to consider I guess.
I've benefitted from such Facebook pages and I've donated happily too. They CAN be a great source of community spirit and it does mean less environmental impact in terms of perfectly good items not going to waste.
But it can be hard for folk to change their views of such things. That they accepted help themselves is sort of irrelevant, it sounds like their circumstances were such at the time they had little choice?
My parents accepted help when first married and before they had a decent income but they speak even now almost 50 years later of how ashamed it made them feel and that they had hoped their children would not need to do so.
Unfortunately shit happens and so all 3 of us have been in relatively dire straits at points - either financially or otherwise - and needed the kindness of strangers.
Which we were grateful for, but it's still horrible having to do it.
She could have handled things better, you and dh could have spoken with her before asking for the trousers...
You're ALL going through a lot at the moment. Try and give each other a break and be a little more understanding than usual? And yes I mean mil in that too
I'm so so sorry for all you're all going through it's really shit and stressful and expensive, I've been there with various relatives sadly. I don't think until you do you really understand the impacts of a long term illness like this.
Wishing your dh a full recovery and you all the strength and compassion to cope and hopefully soon some peace of mind 