Should it be 'Sheik' or 'Sultan'?

There were sheikhs in the Ottoman Empire, but they were only local arab chieftains. The Turkish rulers alllowed local strong men to have all sorts of titles, provided they kept the peace and paid their taxes.

There was only one Sultan, however, and he was the capo di capi -- Numero Uno. .The Ottomans' ancestors, 11th century Turkish intruders from Central Asia, brought with them the belief that leadership was a divine right bestowed on a chosen family. Potential male heirs fought each other at the time of the death of the reigning sultan, and to the victor went the sultanate. The practice developed that the sultan would often kill most of his male relatives—careful to leave at least one alive as a future successor—in order to avoid a rivalry within his own family that might endanger his reign. After the practice of sending princes to the provinces was ended, princes were kept in a special place in the palace called the kafes (Turkish for “cage”), where they generally spent their days in idleness among the women of their harems. As a result, when they came to the throne they had no practical experience in governing. In accordance with the Turkish proverb, “the fish begins to stink at the head,” this lack of leadership became a serious factor in the decline of the empire.

You can also use the word seraglio as well for the living quarters reserved for wives and concubines and female relatives. Early on, the political impact of the harem or seraglio was immense, and the mothers of young sultans exercised power in the name of their sons. This was called "The Sultanate of the Women."

The ruler of the whole Turkish Empire was the Sultan. If your heroine is in the harem of the Emperor, this is the word to use. But he was the only one - there were no minor sultans.

"Sheik" is an Arabic word. There have never been sheiks in Turkey, because they aren't Arabs and therefore don't speak Arabic or use Arabic titles.

Depends in whose harem she goes... if it's a king, particularly the Sultan of Egypt or the sublime Porte (Sultan of Constantinople),the title Sultan is appropriate. Most other local rulers, such as that of Algiers or other Ottoman possessions wear title Dey or Bey.

A normal rich man would just be a shaikh.

Sounds good. Can I read it?

And if there isn't any discrepancies with the title, then I would say just use which ever you think sounds better.

Personally, Sheik sounds, well, more sheek. I would use that one. But there is some definite seductive qualities to being called Sultan.

I've been reading too many trashy novels as of late.

I prefer Trojans myself. Especially with a whole harem. I mean, yeah, purdah is all good and fine, but sometimes they do sneak out when a eunuch falls asleep on watch, and I never know where they've been. Why take the chance?