There's bit of a backstory, and this isn't a MIL issue as she's not doing anything wrong nor abnormal (actually she's being very kind).
Trying to keep it brief:
My mum was a traditional stay at home wife, my dad had a fairly good career until the 2008 recession, his sector nosedived and he unexpectedly died. Not making this a sob story but things were tough, especially for my mum as she had no work experience/qualifications, financial literacy, mental health in tatters, and financially we were screwed as dad had cut back on his life insurance just before he passed. Also I think it's somewhat important to this situation is while I love my dad to pieces he was financial/emotionally abusive to mum. Since I can remember it was drummed into us that we needed to get an education/career for us to be independent. As mum was passionate that we'd never be 'reliant on a man' she was a quite hard, no nonsense, bit of a tiger mum and any whining was answered with 'if you get a good job you can have it/do it'. I started working at 14 and became fairly self reliant.
Fast forward to the present and mum is still struggling financially, not nearly as bad as before but got little disposable income. Us 'kids' have all done fairly well, all independent, good careers, on the property ladder etc and mum is ridiculously proud of us and herself. I'm also really proud of mum and thankful that she installed those morals into us - I can't say i've always felt this way especially as she was somewhat of a dragon!
Now mum is declining in health and she's seemed to have done a 360 in her views (before she's broken up with a few men who've mollycuddled their adult kids).
Small things like I've always picked up the bill if we've eaten out and before she was proud that I could afford to do it (my siblings do the same). We went out to eat with my in-laws and they kicked up bit of fuss with us picking up the bill. It's now caused mum to snowball that she should have done things differently and generally feels like a failure for toughing us up. It's heartbreaking and it doesn't matter how much reassurance we give us she's stuck in this hole.
However, MIL is the complete opposite which I know just comes from kindness but does feel suffocating. She's always offering us money, buying us gifts/things for the house, still does BIL laundry/cleaning, wanting to know our financial situation etc. Our dishwasher is broken, we're happy hand washing as we didn't really use it and MIL caused another fuss in front of mum with insisting to buy us a new one (we did manage to reject the offer in the end as i'm really uncomfortable for accepting money) but just another thing to make mum feel like crap. It's not necessarily MILs actions but comments like 'I remember what it was like setting up home, we couldn't have done it without our parents...'
IL's has very kindly offered to host us (including mum) for Xmas and I know it's just going to make mum feel worse. MIL is always no expense spared and that includes gifts. I reckon she'll spend £150+ on gifts just for me, and probably at least £400 each for DP/BIL/SIL.
MIL is just generally rubbing salt into mum's wound at the moment and it's heartbreaking to witness. Is there anyway I can try to mitigate this or is the only approach is hoping that reassuring mum is enough? I have tried keeping them apart but MIL being oblivious is going over my head to organise these things.