Gosh OP your MIL sounds like my STBX (thankfully) MIL.
She doesn’t like women and has no female friends (not helped by her propensity for trying to shag any man in her vicinity, married or not). She had seven children, the first quickly followed by Golden Boy (who I stupidly married), then four whom she ignored, and finally Golden Girl. DC1 was totally screwed up, GB thought he and she were wonderful on every level, and GG also thinks she’s quite fantastic. The four middle ones turned out to be very normal and have all done extremely well, they became a little unit on their own, not influenced by the vile cow.
All the children bred extensively, and out of each family she would choose one Golden Grandchild, and is now trying to continue this with her Great Grandchildren. Finally though there has been a revolt, and the not Golden Grandchildren now refuse to let her see their children. She would do things like give £20.00 to one child and nothing to the other two.
To a certain extent she wasn’t too bad with mine as they were GB’s issue (I was considered merely the vessel that carried them), and although DS is very much the Golden Grandchild my DDs haven’t missed out too much.
She’s never really been called on her behaviour; one BIL did and she’s hated him with a vengeance ever since. If anyone said anything she'd have a funny turn, and the not-golden children seem to have been desperate to make the cow love them - all to no avail, she still can only bitch about them, they’re either lazy, plain, fat or work too hard. One is now NC and one has very little to do with her.
I used to fantasise about having a go at her, but knew if I did she'd have a “turn” , and could imagine her dying words being “Molecule said....”. The only person she loathed more than BIL was me, all because I married GB. Now we’ve separated she and STBX have found life isn’t quite so much fun, and despite having many children and grandchildren no one wanted them for Christmas, until finally one of the Golden Grandchildren relented.
Anyway the above is not much help to you, save to say that you are not the only one in this position. The Golden Child often doesn’t see what the problem is, and tbh I wish we'd separated much sooner (in my case there was EA, FA and finally it was when it became physical I couldn’t keep going any longer). Funnily enough MIL was proud of this; STBX raped me, and rather than keep quiet she told all the family. I think in a perverse sort of way she was chuffed he could still get it up after 27 years of marriage. This backfired with most of the family wanting nothing to do with STBX so Golden Son is now left somewhat tarnished.
Sorry for the essay (there’s actually much more to say on the subject; MIL is almost unbelievably vile), but I really think you need to remove yourself from this marriage. I imagine neither your DH nor MIL will change, and the less your DD sees of her the better.