Regarding those 12 Second Class ladies lost, I suspect that Finnish passenger Martta Hiltunen might have gone back to her room after he missed getting into Lifeboat #4. She was nowhere near Collapsible D when that boat was loaded and launched only 10 minutes later and no one around recalls seeing her at the time.
In my opinion, i don't think that anyone, male or female, got 'stuck' in their cabin ie not being able to get out when they wanted to. But quite a few probably elected to remain in or return to their cabins because either they did not believe that the Titanic was going to sink or (in the latter case) because they missed getting into a lifeboat. One of the latter could have been Martta Hiltunen, a Finnish Second Class passenger who did not follow her cabin mates Anna Hamalainen and the latter's baby son Wiljo into Lifeboat #4, presumably due to confusion arising from the language barrier. Martta was nowhere in the vicinity when Collapsible D was loaded onto the same davits as #4 only 10 minutes later and so one assumes that she returned to her cabin to wait for the end.
You know, I understand not believing Titanic would sink, at first. Even Lightoller is on record as having not believed Titanic would sink until rather late in the evacuation process; however, at some point Titanic's list was such that I have a hard time imagining that there was anyone who did not eventually become concerned. Under normal circumstances, I would expect them to eventually figure out that there was a serious issue and leave their cabins.
I have less of a hard time believing that some cadre of men and women realized they were likely to not be saved, and the returned to their cabins (or at least to the warm spaces inside the ship) to await their fate.