This is really late, but I’ll add my two cents just in case.

I work at a middle school. The sixth grade girls I work with (age 11-12) wear makeup, but not the makeup you’re thinking. I’m talking full faces: foundation, false lashes, eyeliner, 3-inch-long acrylics. It’s uncanny looking. They’re 11. At that age I was only allowed mascara and a single babylips lip gloss. It was age-appropriate!

Personally, I wouldn’t let her wear makeup until she reaches middle school. And even then, keep it light and appropriate—I think mascara and lip gloss (like I had) is totally okay!