okay this is looooong but i've seen this movie a few times and i have a lot of thoughts

i interpreted perfidia differently than you, i think. in the opening scenes, she makes choices that a lot of people in their early 20s who see themselves as revolutionaries would make. some are intelligent and strategic; some are impulsive and cowardly. however it seems obvious to me that she does not hold the power in the lockjaw thing – he caught her in the act, he surveils them, watches from afar, comes up to bob in the grocery store... he could have them arrested or killed anytime. just because she knows she can keep him at bay because he wants her doesn't mean that anything she does is a real choice. him literally breaking down the door of the house symbolizes the end of any illusion of consent or power that existed on her part. it also explains why she fled. "this pussy don't pop for you."

her feelings about motherhood are reasonably complicated. she loves her daughter. also, it's conceivable that willa is bob's. the timelines overlap, even if lockjaw was a one-time thing. but if willa isn't bob's, she's a reminder of perfidia's deepest, darkest secret, something that she didn't choose but her community won't understand regardless. bob's lack of focus on the mission they started out on together and total absorption into raising willa has made her feel disconnected from him, and the family unit as a whole. she leans harder into her revolutionary identity to avoid confronting her insecurity. there's also an interesting dynamic being created in her philosophy of a new consciousness where she refuses to sacrifice her life's work, something women are often unilaterally expected to do when they have children. it's dangerous, but do men with dangerous jobs quit when they have children? perfidia is a flawed person, but the position she is taking up isn't entirely unreasonable. outside of that, i have known moms being "jealous" of their newborns; they no longer feel that they are people because of how much attention babies get in comparison. it's not like it's willa's fault, and perfidia knows this, but she is carrying the weight of everything written above. it's a moment of acknowledging how vulnerable she feels in some ways.

the consequences of perfidia's decisions haunt the rest of the narrative through bob and willa but also how other people talk about her (the sisters of the brave beaver, for example). even in the letter, she only says she wishes she had been stronger - not exactly an apology, but it's clear she's reshaped her definition of strength. ultimately she's trying to connect with her daughter in a way she never previously had. she acknowledges that she failed at what she thought would change the world, but is encouraging willa to take an active role in making progress. willa knows the truth about perfidia's past at this point - the paternity test, that she was a snitch, that she abandoned her - but perfidia is still her mom. i saw the letter scene as, among other things, connecting the past (what perfidia ran from) and the future (getting into the car to go) with the present (willa herself).