This chapter's not good news for the "Marisa can fly without her broom" faction - seeing as it shows Marisa dangling from it. Her body isn't floating, but the broom is. She does effortlessly right herself soon after, but maybe her balance is just that good. She's had a lot of practice, after all.
I find it unlikely she's completely screwed if she ever lost her broom - she probably has some sort of failsafe on hand - but the difference between her, the self-styled ordinary magician, and Reimu (shown very shortly after effortlessly floating) is showcased in this chapter so conspicuously that I have to assume it's intentional.
If it's true that in every Touhou game, the only thing standing between Marisa and a deadly bout with gravity is a glorified wooden stick... That would make her even more of a thrill seeker than I had previously suspected.
Akyuu's quote from Perfect Memento that suggests Marisa's use of the broom is a stylistic choice, rather than a necessary one, is doing very heavy lifting. It's from 2006, after all. Still - if Marisa can use a magic broom to fly, she can probably use other magic tools as well, in a pinch. She always has her mini-hakkero on hand, and has used it for propulsion in spell cards (Blazing Star), so that's at least one emergency option we know she can fall back on.
Anyway. Another surprise is that Reimu still seems to believe her disguise is capable of fooling anyone. Granted, it does cover her armpits. That alone makes it a rather excellent disguise. But why does she think she even needs one? If she wanted information from the villagers about rumors of youkai sightings, as the Hakurei shrine maiden in charge, she could just ask. Why the secrecy? Does she think if the villagers knew it was her asking, they would keep quiet because they'd feel sorry for the youkai who would get their asses kicked?