She is the daughter of the court blacksmith, grew up together with the prince and decided to get married to him a couple of times before the age of ten. luckily for the court people, it turns out she is not attracted to men and now they are just childhood friends. She considers this holy quest quite dumb shit but i mean who wouldn't help their best friend get a bit of independence from their family?
The journey is to some risk to Jules herself, as the clergy is not likely to accept her accompaniment of the Prince. It is still questionable if she will still make it into a full member of the clergy once she gets back. Jules is also not entirely convinced the prince actually had a divine calling. However, if your childhood best friend needs to sneak out and see the world before he's too cooped up by responsibilities... Well, of course you would join them!