Bloody hell Coco
My MIL is in a similar vein.
She did her utmost to try and spoil our wedding day. I won't list all the things she did, it would take an entire thread, but by the end of the reception my DM had heard enough of me being openly bad mouthed and told MIL to either shut her mouth or step out into the car park to "discuss" it further.
When I had my first mc she said it was shame as she and SIL had only just come around to the idea of me being pregnant. When SIL got pregnant a few months later she made many comments about "finally" having a grandchild then on Christmas Day, of all days, asked "wasn't yours due around now?".
When I got pregnant (was pregnant that day but we hadn't told anyone), when I got further along she was constantly comparing me to SIL but in an unkind way. SIL was glowing, I looked tired. SIL had put hardly any weight on, I'd gained loads. SIL was keeping the sex a surprise, I'd ruined my surprise by finding out. And so on.
It didn't get better once we had DC. She played constant favourites. When I took 2yo DS to her house she would make food for DN and not even ask DS if he wanted any. DN had piles of toys there that DS wasn't allowed to play with. I stopped taking him there when I heard them say "quick, here's ! Hide the toys!" because it was a selfish, petty thing to do a child.
When DS was a toddler she said he reminded her of Cousin XXX. I said yes, because he's a happy boy just like XXX. She replied "no, I meant the other reason...". Cousin XXX has severe learning, behavioural, and mental disabilities. DS was 18mo at the time.
When I was 14wks pregnant she threatened to have me beaten up, told me I was evil, and to watch my back. Turned up at my house and stood on the path outside with her DP, both shouting at me. I was home alone with 10mo DS at the time. Why did she kick off? My DB had called in and found me ill with morning sickness so he took DS out for an hour while I had a lie down. He posted a picture on FB of them at the beach, I liked it, she saw it, she went ballistic that DB was hogging the baby (a baby she hadn't bothered seeing in over four weeks). I had a mmc diagnosed a few days later and while the two are likely unconnected, the measurements indicated that my baby had died only a day or two before the scan (measurements were accurate for dates) so I will always wonder if the stress she caused contributed.
These are just the highlights (low lights?) of a long and complicated history. I am not a bad person. I have always made an effort with her and have forgiven her more times than I can count, I even tried to rationalise much of her behaviour and in return left myself open to even worse.
In short: some people are cunts and will don't deserve to be part of your family.