I agree that she should be able to wax or use cream if it's noticeable. Nothing is worse than being teased about this kind of thing.
I have had dark hairs on my upper lip and extra eyebrow hairs that I've been removing since I was about your daughter's age.
In the summer, I actually use peroxide to bleach my "mustache" hairs. Once they're bleached blond, they aren't as noticeable. In winter, I'm not in the sun enough to make this method work well, so I use creme hair remover. Since your DD is still a kid, start with something mild that is specific for faces. I have used straight-up Nair on my face, but it can burn sensitive skin.
For eyebrows, I use wax strips. When I was younger, my mom used to take me to the salon to get my eyebrows waxed, but when I was on my own in later high school, I didn't want to mess with that or pay for it, so I learned to do it myself.