If it's okay with her employer, it's fine with me. In general, I would say better with mom than a sitter.
When I was about 5 my favorite thing was to go the the beauty palor with my mother. Man, she'd be there all afternoon.
They put me to work man. I was in charge of sweeping up hair and making sure the movie magazines where all lined up nice and even. I'd sort the nail polishes by color and make sure the calendar at the front desk was turned to the correct month.
Just like Kenny Loggins said in "House at Pooh Corner", you'd be surprised at how much should to be done.
I knew more about Liz and Dick from those movie magazines than any 5 year old in town.