That's cute. I don't know how well her hand control is, but you should take her to an art supply store and let her pick out some nice supplies and paper.
If she doesn't have some already, decent paint brushes in several sizes (especially smaller ones) might really help her.
You could check your local library for very simple beginner painting books. She may pick up a few tips that can help her.
At that age I already had a collection of brushes, sable and synthetic, a lot of paints, and had been painting ceramics for nearly five years. I was lucky to have a very artistic uncle who encouraged me and bought me supplies - my parents wouldn't.
I love it! Especially the colors and the expression on the kitty's face.
It does show a natural talent that you don't often see even in adults.
Back in the Dark Ages when I was briefly married, my husband was an artist, and one evening we visited a wealthy couple who had bought one of his drawings. Their house was built around a central hall that had once been a huge barn, and the barnboards were whitewashed. One 30-foot-tall wall of the barn section was devoted to artwork, edge to edge all up and down the wall -- and about half of it had been bought at local school art shows! The lady just had an eye for choosing good stuff, amateur and otherwise. I really admired her taste.
And that lady would have bought this painting in a heartbeat!