Just a note on women on Soviet subs:
The USSR used subs to evacuate women and children from Sevastapol when it was under seize during WWII. Maybe in a non-historical setting the crew decided to keep one of them on board as a cook? Of course, this only helps if the sub in question was based in the Black Sea / Med area. If it was in the Baltic Sea, or associated with the Murmansk runs, or in the Pacific, then she would need another excuse to be there.
Richard