Oh wow OP - i feel the pain! When i first started dating my OH i quite liked my then future MIL whom I thought was outgoing and quite fun. Fast forward 3 years and i started to realise how much mental damage was done to my OH by her when he was a child, my opinion slowly starts to slide but as we were overseas I didn't see her much.
Fast forward another 5 years, marriage and two toddlers, have returned from overseas and i am physically recovering from a serious accident that left me disabled, staying with my parents as a. They have the space and b. They want to help care for me and the kids whilst oh is at work. In laws come to "help" once a month by taking the dcs out for 2 hours so to give my parents a "rest". Every visit dcs are returned 2 hours later covered in dirt, cuts, bumps and bruises, chocolate and icecream and are so hyped up on sugar they don't sleep till gone 10pm, in spite of me politely requesting no sugar every visit.
Then my parents take a much needed holiday and whilst they are away I had to have surgery. So my OH asked his parents if they could possibly help out with the dcs bearing in mind we are constantly bombarded with "oh if we can ever help at all...."and as they only live 30 mins away they came the day before to get some clothes and things (in spite of having their dgc monthly and being very well off, they had only one toy in the house which naturally caused enormous fights as to which dgc got to play with the ONE toy). Whilst at my parents house I was in kitchen and overheard my MIL very loudly complaining to my OH that he wouldn't give her the keys to my parents house saying how selfish he was and how inconvenient what we were asking was. So I came outside and joined the "discussion" where I discovered that she found the plans of them coming to collect the dgc, taking them to theirs for the day, feeding them lunch and dinner, popping them in their pjs and driving them 30 minutes back was far too difficult, complicated and inconvenient and why couldn't my OH give her the keys to my parents house so they could stay at the house all day whilst my OH and i were in hospital and when I got home that afternoon after my operation they could just go. I refused the keys stating it was not my house to give the keys to, at which point she lost the plot swearing at me, telling me the dcs were the most foul children she'd ever come across, how we were all just lazy "f*$%s" and then started blaming my disability on me and it was all my fault!
Funilly enough I requested she leave the premises. I ended up taking a taxi to the hospital and back so OH could look after the dcs. She hasn't spoken to me since nor seen her dcs, her choice. It has been 7 years and they are the only dgcs she'll ever have!
So yes, I sympathise and yes I needed to mil bash but for a very good reason! Best of luck. 🍷🍷🍸🌷