Awww!!! Saint puppies are the absolute cutest! I am so excited for you, she's going to be an amazing family dog for you.

I completely attest to the fact that Saints (and Newfs, and Pyrs, etc) eat very little for their size. I know a huge, fit, energetic young female named Strudel, and she eats 1 1/2 cups a day of premium grain free kibble. She refuses to eat anymore than that and she's of perfect weight.