Thankfully this story is about my ExMIL. My current MIL is more baffling than cruel, but I don't mind that.
My ExH and I met at university and this happened before we were married, but we'd been together a couple of years by then. This was the first time something weird had happened and it seemed to come completely out of the blue.
ExH and I had a visit organised where we travelled across country to ExPIL's house, from where we'd travel all together in the same car to ExH's Aunty & Uncles to stay overnight for a barbecue party that they'd arranged in celebration of ExH's cousin's graduation - lovely. ExH and I were both looking forwad to a nice party and trip away because I'd just finished my last exams at uni too.
As planned, we headed from ExPIL's house to the Aunty's house in one car, about another hour's drive away, deep into the countryside somewhere - I had no idea where and this was before GPS phones.
Soon after we arrived, I realised something wasn't quite right. There was a giant marquee in the grounds of their enormous house, caterers and a large live band setting up on a stage in the marquee. I was told we were going to a barbeque, but it wasn't, it was a black-tie ball with over one hundred guests.
ExMIL innocently smiled saying "Oh no, the barbeque is tomorrow lunchtime. I'm sure I told you about the black tie evening ball". She then produced from the car a tux and bow tie for my ExH, apparently that he'd left at home from his 6th form days and still fit, but I was expecting a barbeque and had no ball gown with me! I was expecting to just wear some nice trousers and top. Luckily I had a summer skirt in my bag but ended up having to wear it with a casual top and casual shoes and my hair wasn't exactly ready for a ball!
We had no way of going anywhere to get something for me because we'd travelled with ExPIL in their car and weren't even sure where we were. ExBIL then turned up with his girlfriend who had clearly received the message about the need for ballgowns. I felt so stitched up.
All the other guests gave me funny looks, some of them spoke to me in a pitying voice, clearly thinking that I couldn't afford a dress. I had to sit there all night trying not to be noticed, when it should have been my opportunity to meet all of ExH's family properly. I was completely mortified and humiliated and I don't think I ever really got over it. The most frustrating thing for me was that I'd just bought a ballgown the week before for my own graduation ball at university.
Thankfully she never did anything so cruel again after that. I think ExH gave her quite a talking to, but despite this, he still wore the tux that she brought for him rather than his casual clothes in solidarity. Bastard.