@crinrictThanks for your suggestion. I tried this, and it seemed to work, and I went through all my cc, gradually adding it in groups until I'd re-added them all. I realised it might not've been the gender of the sim but that specific sim that was causing the problem.
So, I reloaded her from my library, and tried again. Sure enough, what I could see on a random sim was not visible on her. So, I removed all cc from her, and still the problem persisted. I made her an identical twin using the genetics feature, and still the problem persisted even on the twin. I reloaded my game without any mods or cc, loaded her from my library, saved her so she had no cc, then loaded the game back up yet again, and the problem persisted.
This is extremely odd, but as it's this sim specific, I'll just keep playing as is. I appreciate your help, and I'm sorry I didn't do more testing in advance.
I'm not sure what was going on with my older sims from my library, as the problem appears to no longer be there - maybe it never was, and I didn't check properly.