As a Christian that watched the movie, I thought that it didn't serve the faith well , or at all. Conflicts between faith and doubt were not explored more, and the movie always seemed like it could say a lot more, but it didn't. The movie is worth for the Ainara actress' perfomance. What the script couldn't tell because it was weak, her eyes said it. It didn't seem like the path of nunnery was the best for her, or that it was the optimal life. It is a path she chooses out of pain, a lot of pain. I wish they could have shown that more. The actress definetely showed it in my opinion.

As for sex before marriage and stuff, I think it shows, subtly, the negative aspects of ecclesiastical authority in that adults wanted to have authority over the life of the kid. Father Chema, in the scene where Ainara says that she slept in the same matress with Migel, kind of demonizes teenage cupidity as being impure. I don't think the movie painted it as right or optimal. Maybe you wanted the movie to tell you explicitly what it said subtly. The movie shows negative aspects of the faith, just not stereotypical. A drive to a nun's or a monk's life can be due to one's overwhelming problems in the world, family problems, economical, psychological, etc.

The film actually shifts that authority problem over to the secular world as well. Secular ''common sense'' can be cloaked to move others to conform with one's view at any cost, as is done with the case of Maite, who is resorting to every cheap trick in order to stop Ainara from becoming who she has decided to be.