Mongrelmind observes that in MDZS as opposed to CQL, Lan is gender-segregated. The world of MDZS also does not necessarily feature normative marital queerness (though we don’t exactly know that it doesn't either, I believe?). However to get more women in the narrative, CQL (which is no clearer on the typicality of queer marriage: we don’t see anything to either suggest or to disprove it as a normative feature of the culture) opted never to say anything on gender segregation, and to include several moments that make it seem as though the lectures are coed. Yanli not only attends, she’s shown in the classroom (not just for the opening ceremony, but thoughout). Wen Qing also shows up in the lecture hall, and while there’s less camera focus on Mianmian, I believe she’s consistently there (Mongrelmind suggests she’d be allowed regardless of other arrangements, as Zixuan's emotional support lesbian). There’s a suggestion that Cangse Sanren may have taken part in lectures herself.
Yanli might be staying in a gender-segregated dorm, but it’s not terribly clear. She’s certainly sharing meals and spare time with her brothers. They eat together late at night. After the Qixi betrothal fight, Wei Wuxian goes to see her at what looks to be the same complex they’ve all been staying in, so I think it likely the Jiang contingent has just been afforded some shared huts.
Arguably, I can’t think of any Lan female disciples shown in frame (here or elsewhere). This is fairly hard to make out in the background, given the relatively unisex style of dress and characters' long hair across the board. Perhaps guests are not segregated, but Lan disciples are. That would be a matter of interpretation, however, and I might even suggest, given CQL Lan’s evident comfort with including visiting female disciples, that such a reading would run against the grain. You could claim it’s like ancient Athens extending license to foreign women that they didn’t extend to their own female population, but that reading would be a rather active choice.
At that point, I’d ditch the book’s gender segregation canon (unless you need it for a given fic) because it’s not necessarily the case and does not spark joy.
Maybe there should be a checklist of what elements are true in which canons, and why we think that? In a fic I’m happy to engage with a mash up, but the chronologies for the various canons (book, manhua, donghua, live action, Chinese audio play, Japanese audio play) are fairly different, as are core elements regarding how demonic cultivation works, et al.