It's a joke.
Oh. Huh. Was it funny?
Though Rodgers and Hammerstein worked with Martin to create the role of Maria for her, after she departed they agreed that the piece would be served best by going much younger than middle aged for the role.
Sutton can easily pass for 30s, I think. It also depends how they cast the Captain. When there's a visible 20+ year different, it starts looking skeevy. And then there's the whole Liesl thing, where it's already a little funny that she goes to a nun for relationship advice, but when they also appear to be similar in age, it ventures into a grey Freudian haze.
But even if Sutton didn't play Maria, she could easily steal the entire show as Elsa Schraeder. I'd pay good money for that alone.
"What can you expect from a bunch of seitan worshippers?" - Reginald Tresilian