I thought she sounded sweet enough; she was at least closer in age to the character than many others who have played the role of Maria before her. But I think you might have a good point, she might be good in something like Annie Get Your Gun or Oklahoma for instance.
I suspect that she (and many C&W aficionados) think it sounded okay.
Im not a C&W fan. That is why I was surprised that she did as well as she did with the singing. It was good, much better than I expected, but certainly not great. And thats why the performance of Audra McDonald stood out so well IMO.
But as far as Maria being sweet, in truth the real life Maria was not exactly sweet herself. She was a very strong willed and rather domineering woman, one prone to fits of temper tantrums and rage and very controlling over her husband and the children. And it was not initially a great romance. Maria Von Trapp in her own biography said that she was not in love with the captain when she agreed to marry him but married him only because she fell in love with his children. She came to love him later but their marriage was not exactly a love story for the ages.
And after many years of suffering under her iron will and desire to keep the Von Trapp Singer together and her other family enterprises together, some of the children who were well adults by then, finally revolted.
But on the other hand the real Captain Von Trapp was not the man portrayed in the stage musical or movie either. He was a much kinder and gentler and kind father than he was portrayed and pretty much let his second wife Maria take charge of the familys business affairs. To her credit, if not for her, after they lost all their money during the Great Depression they would have remained penniless as Georg Von Trapp, being from an aristocratic family, didnt like the idea of actually having to work for a living. Maria on the other hand was always looking for ways to economize or make a buck.
I love the musical but I also understand that it takes great liberty with the real story of the Von Trapps. But the real story might not make for such a sentimental musical. (Oh and FWIW, the real Von Trapp Family singers did not sing snappy show tunes but rather somber religious madrigals and very old traditional Austrian folk songs - no rain drops on roses or do a deer a female deer or climb every mountain.)