Honestly, I wouldn't even call it jealousy to get miffed that your SO keeps inviting other people into couple time, especially for someone like Bocchi who barely feels at ease with just herself and those she's close with around, never mind the 'we had plans but you just agreed to go do this other thing' situation.
Granted, the sentiment of 'try to not smile so adorably in public, 'cause then other people will fall for you' is definitely proper jealousy. But Hitori doesn't push it and as a whole this draws pretty well on their characterizations such as to be believable. Bocchi's anxiety and catastrophizing would undoubtedly extend into her headspace about her relationship were she in one, and Kita is enough of a habitual people pleaser that I could see her having difficulty prioritizing her dates over other people's requests.
In summation, I find this work both cute and plausible.
