I would say an unreliable narrator because that kind of narrator is the best at keeping secrets from the reader. If that's not an option, then a restricted narrator because they only know a limited amount of information.
Whether she would be imprisoned
Dukes and duchesses ruled areas called "duchies". These duchies were rarely their own countries, and usually parts of a larger sovereign country ruled by a king and queen. So there would be one king and one queen ruling a country, for example, but there could be several dukes and duchesses ruling smaller territories of the country. Dukes and duchesses are always lower than kings and queens.
Barons and baronesses are the lowest ranking of the nobles. I'm not certain what power they had but I'm pretty sure the title was mostly honorary.
A basic hierarchy would look something like this:
Emperor/Empress
King/Queen
Archduke
Grand Duke
Prince/Princess
Duke/Duchess
Marquess/Marchioness
Earl
Baron/Baroness
I'm pretty sure I left a few titles out, but hopefully that answered your question.
