I’ve read at least three different books that were based on the book of Esther, from the Bible, plus a movie.
They all have one thing in common, in that each girl’s meeting with the king is a social one. Usually they just have dinner, or spend the evening talking. They don’t spend the night, yet the original story pretty well lets you know the king was giving each girl a test drive.
In the morning they could either return to their homes, presumably with a royal seal of approval and none the worse for the wear, or go into the king’s harem.
Are there any novels that actually have Esther and the king having sex during her visit to him? I’m not sure how to search that way.