[Rune~Grey]

As far as things go, I think that Rosette is something of a different case when it comes to being a 'nun' per se. The Magadala Shuudoukai is a religious sect in the same was as the Templars were a religious sect - they're a militant order, so you'll have some different sorts of people there.

Spoiler:

Then again, Rosette isn't the best 'nun' in the world either. A big reason why she's even in the Magadala Shuudoukai to begin with is because they're helping her to get what she wants - that mainly being the resources to try and locate her brother Joshua. When you look at it, she's very far outside of the boundaries of what the Shuudoukai would consider to be 'acceptable' - her behavior tends to go a little over the top, and she has a contract with Chrno... who isn't exactly what we call a 'normal human'.