The Menu (2022 film)/WMG

The food was drugged, which is why no one was screaming in pain at the end
Chef Julian orders Margot to eat when she hasn't "touched [her] food," in his words. He looks genuinely concerned and says it's because he takes his craft seriously. It could also be that.

Ms. Westervelt's first name is Margot.
This is why Julian was absolutely certain that our Margot, whose, isn't using her real name. While it's not impossible that Tyler would choose a woman for his date that has the same name as his ex, it is unlikely.

Tyler was suicidal after his breakup with Ms. Westervelt
That's why he was very eager to come, despite Clues: 1. His nonchalant reaction to "The Mess", namely Jeremy's death by suicide. 2. Tyler only shows sadness and remorse when he quietly admits that Ms. Westervelt broke up with him, as Julian presses himself for answers on why he brought Margot. 3. He.

Julian had a personal vendetta against Ms. Westervelt
He has different reasons for all the guests being there: his mother being an abusive drunk, the tech bros representing his bondage to Doug Verrick, the restaurant critic and her editor for a co-dependent ego feeding relationship, the "regulars" for not appreciating his craft, Tyler for ... and George for starring in a bad movie. But Ms. Westervelt? Who was she? And why was she included in the Menu? Julian never elaborates, only expressing disbelief that Tyler brought a "substitute" date. He even seems horrified that Tyler invited an innocent woman into this mess, telling Margot that she's "all wrong" after she realizes they are trapped in a bad situation. It's likely that Ms. Westervelt was either one of the wealthy "takers" or someone that Julian felt crossed him personally. She was wealthy enough to afford Hawthorn, as implied by her name being on the seat, but we don't know if she was a nice person.