I'm in pain.
I know this is a fictional story but taking an Empire, such as the Ottoman Empire, and making a story out it, I would feel like getting the little details is important. (1) "Nobles" of the empire did not send their daughters to entertain the Sultan. A Sultan was not allowed to favor one of his "nobles" more than the others. (2) The Sultan did not "marry" anyone outside the harem. So, no fiancée. I say the term marry loosely because most Sultans didn't marry, they have a Harem. Why would they need to marry?
The same can be said for a prince of the Ottoman Empire, they had a harem of their own, small one, but still they had a harem. So no fiancée here either.
The only that is close to accurate is the way the FL is acting, keyword close. When a girl is brought into the harem, they were typically taken at an age before puberty begins for them. Also they come into the palace naive and scared. They are dumb, illiterate, and from a peasant background with no primary or secondary education. Everything they learned was decided by the the Sultan and/or the Head of the Harem (usually Valide Sultan--the Sultan's mother). The most popular subject they were taught were writing, sewing, poetry and dancing. That's it. Everything else, such being able to manipulate and deceive others they [the concubines] taught themselves in order to survive in the Harem. The female hierarchy followed the pattern of odalisques (virgins), concubines ("one night stands"), ikbals (favorites), and kadins (favorites "wives").
Honestly, with the way the FL acts, I'm surprised she is still even alive, even if she led a quiet life far away from the Harem (it's a do or die life after all). If she lived that quietly, she could have still been chosen as a servant to someone else in Harem, such as a favorite, a caretaker (not nursemaid) of a royal child, or a servant to the Valide Sultan.
And when other people in the comments talk about "this is another Stockholm Syndrome story" in a sense it is. Being brought to a palace at a young age and basically being taught that your only purpose in life is to entertain the Sultan and (if you're lucky) have his children.
This was too freaking long, bye.