It's called Pagan's Daughter (published as Babylonne in the US), and is the fifth in a series called The Pagan Chronicles, written by Australian children's author Catherine Jinks. The first four books focus on a Christian Arab squire (later ecclesiastical scholar and canon lawyer) called Pagan Kidrouk, who is displaced by the Third Crusade and winds up in Languedoc. (He's the dude in the icon I'm using here.) Unsurprisingly, the fifth book is from the point of view of his daughter, Babylonne.

Pagan is my favourite fictional character of all time, Una (one of the point-of-view characters in Romanitas) is my second favourite, and both series of books were really formative for me, although I read the Pagan ones a lot earlier.