REVEREND MOTHER: Maria, it seems to be the will of God that you leave us.
REVEREND MOTHER: Only for a while, Maria.
When the decision is made to send Maria to the von Trapp home, Reverend Mother attributes it to the will of God. (We assume she did a lot of praying about it before she came to that decision.) She knows that presenting it as God's will will make Maria take the plan seriously.
MARIA: "When the Lord closes a door, somewhere He opens a window."
Even though she's upset at being asked to leave the abbey, Maria tries to see God's role/presence in her new journey, just as the Reverend Mother suggested. For a devout person like her, this gives her confidence that things will work out, even though she's scared to death.
MARIA: God bless the captain. God bless Liesl and Friedrich. God bless Louisa, Brigitta, Marta and little Gretl. And oh, I've forgot the other boy—what's his name? Well, God bless what's-his-name.
Even though she's left the abbey, Maria's still devout. Praying by her bed on her first evening in the von Trapp house, she's careful to work the family into her prayers. Prior to leaving, she'd been afraid that would mean leaving her faith behind. Sounds like Maria's God has a sense of humor.
REVEREND MOTHER: Did you let him see how you felt?
MARIA: If I did, I didn't know it. That's what's torturing me: I was there on God's errand. To have asked for his love would have been wrong. I couldn't stay, I just couldn't. I'm ready at this moment to take my vows. Please help me.
Maria's not using her religious faith in a very healthy way here. She's using it to avoid dealing with a huge emotional dilemma. Inside the cloister, romantic problems don't exist. Fortunately, the Reverend Mother won't let her get away with it.
REVEREND MOTHER: Maria, the love of a man and a woman is holy, too. You have a great capacity to love. What you must find out is how God wants you to spend your love.
MARIA: But I pledged my life to God. I pledged my life to His service.
REVEREND MOTHER: My daughter, if you love this man, it doesn't mean you love God less.
Reverend Mother tries to assure Maria that there are other forms of holiness—and that loving Captain von Trapp isn't a betrayal or abandonment of God. Maria isn't immediately convinced, but eventually she realizes she needs to go back and face her feelings. It's cool that a celibate cloistered nun like the Reverend Mother would be so wise and open-minded about romantic relationships.
REVEREND MOTHER: God be with you.
Reverend Mother offers this blessing to Maria as the von Trapps are fleeing from the Nazis. She's been instrumental in helping Maria keep and redefine her faith as necessary throughout the story, so it's fitting that she plays a role in the biggest challenge Maria will face. The Reverend Mother is a really centered, calm person in the film. You can see that her faith totally guides her life and gives her serenity. She's completely predictable and consistent in her responses to everything. Where do we sign up?
SISTER #1: Reverend Mother, I have sinned.
SISTER #2: I too, Reverend Mother.
REVEREND MOTHER: What is this sin, my children?
(They hold up wires they've yanked out from the Nazi soldiers' car engines.)
The Reverend Mother's knowing glance at her nuns lets us know whose side God is on according to this movie.