Enter Stone's Abigail: A once noble woman whose father sold her away to a man during a card game. She's cousin to Sarah and comes seeking work, but her larger goal is to get into Anne's good graces and somehow win her title back. At the outset, we're rooting for her, and that's largely thanks to our perception of Stone. Likability is an overvalued quality, in women especially, but Stone has made likable an art ever since she first broke out in Superbad. It's why she could carry a teen comedy on her shoulders in Easy A and why you want her La La Land ingenue to nail that song about Paris.
Abigail is savvy, but seems helpful rather than conniving. Stone told The Hollywood Reporter that she nearly decided she didn't want the role after reading first 30 pages: "I was like, 'Oh, Abigail's just going to be this sweet kind of girl, the victim, a servant to these people.'" Meanwhile, Weisz's Sarah is outright cruel to Anne. She insults her makeup, calling her a badger. She refuses to pet her bunnies, calling them "macabre." (She's not wrong.)
Still, as the narrative progresses, Stone starts to peel back layers of her innocence. She treats her suitor (Joe Alwyn) like a rag doll. Her form of flirtation is kicking him in the nuts. And she begins to scheme -- not just to get in the Queen's good graces, but also to bring down Sarah in callous fashion. Stone ever so slightly curdles those qualities that we inaccurately perceived as appealing. The glances that Lanthimos keeps showing turn from inquisitive to malicious, like when she stares up at Sarah, naked, from Anne's bed.
Hers is a pyrrhic victory. Abigail gets her good name back, succeeds in banishing Lady Sarah from England entirely, and takes her place by the queen's side. But you soon realize Abigail's interests have always been shallow, whereas Lady Sarah, through all her curtness, has something resembling benevolence in her soul. Sure, her relationship with Anne is transactional, but she also doesn't coddle the Queen, refusing to buy into her delusions. Sarah may be manipulative, but she tethers Anne to reality, and that, in a strange sense, is love. Abigail never accomplishes that, despite her posturing.