Miss Beam was all that I had expected middle-aged, authoritative, kindly, and understanding. Her hair was beginning to turn grey, and her round figure was likely to be comforting for a homesick child to look upon.
Here, I think "her round figure" means the "fullness of her figure". But how exactly would it be comforting? (Especially when in movies, the bad guardians are mostly represented by big, fat people.)