They were not at all undereducated as ladies of that class were supposed to be generally knowledgeable to hold a conversation on level. From literature to classic music, from managing a stately home to organizing social events.
They may not have a professional qualification to be a nurse, or a train conductor, or a secretary. But that never was the purpose of their formation. Camilla went to France to train her French language in daily practice. Not because she was planning to live over there but because it was de rigueur for ladies of standing to have a broad formation and preferrably being able to speak more languages.
Let me compare the two sisters with the four daughters of Queen Juliana: like the two British ladies, their four Dutch contemporaries never needed any day of work. Simply because there was no any need to have a professional career. When such a career never was pursued in the first place, it was logic that these ladies were "prepared" for a life without a job indeed. A total different world with many of today's royals.
I am sure that all these princesses were (are) intelligent and socially very agile persons and indeed were prepared for such a life.