I don't know if I'd show a 10 year old Bouguereau. If you make your sister well aware that paintings like that take a lot of work and a lot of practice, and it's not something you do with Crayola, then maybe. Otherwise a little kid will just reproduce something and say "it doesn't look like the painting". Then again some kids reproduce it, it looks iffy, but they see it as a perfect reproduction.
You could also help her do some artwork that lets her explore different ways of depicting subject matter she finds interesting, help her find a media she really enjoys working with, and give her your support with whatever she chooses.
Doctors heal you, Artists immortalize you.
"Those who can, do. Those who can't, teach" - bullshit.
The usual staples for anatomy: