Initially Emma Russel was with Alan John in Godzilla: King of Monsters. Did they have a fallout between them? Did she change her mind about the initial population control plan?
According to Wikipedia:
Emma realizes the destruction Ghidorah and the other Titans will bring to the world is much worse than anything that humans could inflict
According to Fandom:
Emma eventually starts doubting that Jonah's goals are as effective as he says they are, and suggests that they quit the operation
From what I remember of the film, it was pretty obvious that Emma changed her mind and decided that the plan was not a good idea. She may have been swayed by her daughter Madison.