I have a 10 yo who has had orange, red, blue, and green hair at various times. We use Manic Panic -- it washes out in about 6-10 washes. He has sandy brown hair, and the light colors don't take in his hair.
I think the toughest thing will be that you'll have to significantly lighten her hair, as PPs noted, but that when the hair color washes out, the lightened hair will still be lighter. And as it grows out, she'll have lighter hair at the end and dark roots.
The chalks are useless.
If you don't want a permanent color change, I think a clip-in extension is your best bet:
https://www.claires.com/us/hair/fake-hair/?cgid=49