My parents were hoarders. It was horrendous.
My DM was very mentally unwell and went to charity shops, signed up for 'collectibles' at the back of Women's Weekly and was conned into parting with huge sums of (my self employed DF's) money for absolute tat.
Going though the house after she died was awful.
There was no distinction between sentimental family photos and keepsakes and the toot she bought - The sacred front room, where only the best visitors were entertained, looked like a second hand shop.
Wedding photos shared space with a novelty duck hairdryer, overpriced, worthless, modern reproductions of vintage Matchbox cars shared space with collectible teapots, broken jewellery and all of it with price tags still attached.
Tracking down important paperwork like birth, marriage and naturalisation certificates for the registry office, coroner and funeral directors was a screaming nightmare - they were found in multiple places under the stairs, behind the boiler and in kitchen drawers.
She couldn't resist what the sellers told her were 'bargains'. Fabric which she just folded into drawers, net curtains which were never put up, strange looking clothes which fitted no one, 'charity' packs of wondrously expensive wool, bundled with a badly photocopied jumper pattern and a letter of thanks from someone in Nepal (yeah, right)
It was infuriating, because it wasn't cheap and she'd left DF with real financial issues which he had to deal with until he died.
As much of it was filthy, broken and beyond worthless, there was no way we could get any price for it and most of it was thrown out.
Tens of thousands of ££££ wasted.
Thankfully, she never got a credit card.
DF hoarded stuff for his work. The garden had three sheds and looked like a salvage yard.
Broken tools which shut down after 5 minutes use, old sanders which no longer held down the paper and gouged the surfaces, old bits of architechtural salvage, 'nice' bits of good wood, old imperial tools when everyone went metric - some of it went for scrap (lead, tin, pewter, steel and copper), some went to people who wanted random stained glass fittings or a lorry tyre turned inside out for a plant pot.
It was funny and WTF???? all at the same time.
Your DM is wasting money, creating a vermin and fire hazard, preventing her own husband from using space he's entitled to and abusing you in the process.
If she gets even one bag of her filth through your front door, there'll be an avalanche to follow.
Vintage stuff may look cute in internet pictures, but corroded copper is toxic, painted items could be lead and safety standards have improved.
There are a lot of prams and buggies that could trap and amputate fingers, cot mattresses that give off toxic polyurethane fumes or moulds, cords, pom poms or tassels that could strangle or choke a baby and old electrical items are just fit for a skip - who knows if they're safe?
She needs help to sort through what might actually be useful and what needs to be skipped.
Washed clothes could be sent to charity shops labelled as rags but most of it would not even be recyclable.
You have my sympathy OP, you are not alone.