Worth noting that this thread is mostly a group of men commenting on the appropriateness of a woman playing a role. I'll say no more, but this is what women always say about Hollywood: men decide what they can and should play.
For the record, she looks great in the photos. Maybe Belle is a woman who never married and finds meaning and love in early mid-life. Maybe the story deepens, her relationship with her father, being isolated in a town as a single woman. Who reads.
If she can still sing it, who cares?
"I'm a comedian, but in my spare time, things bother me." Garry Shandling