Mrs. Wormwood, Matilda's mother, is one of the villains in the books, but she pales in comparison with the two other villains: Matilda's father and the Trunchbull. Mrs. Wormwood is a bad mother, but she's not as bad a parent as Mr. Wormwood is.
Don't get us wrong. She's awful. But her worst quality is that she just doesn't give a hoot about her own daughter. As Matilda tells us, "'She [my mother] doesn't really care what I do'" (1.41). She ignores her children, doesn't support them, and sides with Mr. Wormwood whenever she has to pick a side. Not that she cares.
She's way more interested in playing Bingo and watching nighttime soap operas than she is in spending time with her family or developing a career of her own. She doesn't even really cook for her family. Some nights they have TV dinners, premade food, and other nights they have takeout fish-and-chips. Talk about lazy parenting.
It's worth noticing that while Matilda says she's going to play pranks on both her parents whenever they behave badly to her, the pranks we read about in this book mostly target her father. The ghost-parrot scares everybody, of course, but it makes Mr. Wormwood look the worst, not Mrs. Wormwood. It's Mr. Wormwood who ends up with a hat stuck to his head, and Mr. Wormwood who gets his hair dyed the wrong color.
Instead, Mrs. Wormwood suffers by association. It makes her sad that her husband looks silly, and that's about the deepest thought she has in the book, but Matilda never targets her by herself. And Mrs. Wormwood doesn't deserve it as much as Mr. Wormwood. She plays a much less active role in terrorizing her daughter.
She deserves some punishment, though. She doesn't step up and defend Matilda when Mr. Wormwood bothers her, and she doesn't help her daughter develop her awesome mind. That's what makes Mrs. Wormwood a villain—she just can't bring herself to care about her own daughter.
Mrs. Wormwood also values outsides more than insides. Naturally, like her vain husband, she thinks her own appearance is the ideal one:
Miss Honey looked at the plain plump person with the smug suet-pudding face who was sitting across the room. "What did you say?" she asked.
"I said you chose books and I chose looks," Mrs Wormwood said. "And who's finished up the better off? Me, of course. I'm sitting pretty in a nice house with a successful businessman and you're left slaving away teaching a lot of nasty little children the ABC." (9.43-4)
Lovely. Suet-pudding, for those who are curious, is a British delicacy made with beef fat. It's not really a dessert, and it's definitely not something you want associated with your face. This statement, then, shows us that Mrs. Wormwood has a warped worldview. She's either too lazy or too stupid to think straight.
She thinks she's hit the jackpot by marrying Mr. Wormwood, "a successful businessman," and been left "sitting pretty in a nice house." It's all right if you don't mind being married to a "twit," to use Mr. Wormwood's own word, and if all you care about are soap operas and Bingo games. But wouldn't a person with some brain cells find being married to Mr. Wormwood depressing?