Brian Formo’s review published on Letterboxd:
There are two markings done throughout the film. First, Cassie's (Carey Mulligan) markings in her journal where she goes out to a bar or club, pretends to be blackout drunk, and then allows herself to be taken how by a man to test him; if he makes a pass while she pretends to be passed out she'll teach him a lesson after revealing she's stone cold sober, if he doesn't let her call a ride home, she'll teach him a lesson after revealing she's stone cold sober, etc. Her journal is full of tally marks. And when I mean full, I mean full; each night is apparently a success.
The other markings are done by the filmmaker, Emerald Fennell, as roman numerals that appear on the screen that kick in the part of the film that works best: Cassie's escalating revenge against the individual people in the collegiate system that (students, administrators, lawyers) disregarded (or outright mocked) her best friend's rape accusation and whose lives all continued while her's did not. It's the appearance of a former medical school classmate (Bo Burnham) who is now a doctor that kickstarts this plan for her. Cassie starts to let her guard down for a potential relationship with him, while hatching plans to attack various people from their collective past.
The tally portion of the film is very broad speaks its truth so matter of factly and, though it allows for some cameos for former teen stars from The O.C. and Superbad as they get skeevy, it's an unfortunate inclusion overall. It keeps us at a distance from ever getting to know Cassie outside of the established facts: dropped out, depressed, feels guilty for not being there the night her childhood friend was assaulted. I say this as someone who was abused, who knows others who have been abused, that this reductive positioning of her entire character being defined by what happened to someone she loved does not a compelling character study make. And for such a serious subject, the surface level approach often makes Promising Young Woman feel more like a blog post than a character study. But that ending is so genre-narrative tight (from video file onward) that it makes me wish we knew Cassie more.
Ultimately, the roman numeral portion makes many of the same points about consent but it makes them better because they push the narrative forward to its blazing finale. The roman numeral revenge portion also lets us see Cassie interact more outside of her nights of entrapment. Because the ending is so well done it makes me wish the film had skipped the broad and flimsier night out stuff and used all the extra runtime that would then be afforded to it to explore the two main characters more, to spend more discomforting time in what becomes the third act, and to let the shock of what happens there linger longer before the payoff.
Make no mistake, everything that happens from the classical string slowdown of Britney Spears’ “Toxic" onward is decent. But for me, it doesn't resolve the feeling that there are two short story ideas combined into one film, and I don't know Cassie in either of them.