I had children at school asking about my moustashe (the boys were just jealous, I reckon) and small children asked when I was an adult. One reason why I don't want to work with 5-year-olds.
8 years old is NOT too young for waxing if the alternative is bullying and rudeness. If your daughter is dark-skinned then laser treatment may not work brilliantly well, but regular waxing will make the hair appear finer. And give her some self-confidence.
It's all right you saying "stand up for yourself" and "everybody's different" but when all you want to do is look like a normal girl and fit in, it's hard having a moustashe. Should I have a daughter with a hair problem like mine then I will have no problem paying for waxing as soon as she requests it and laser when she's old enough (in the UK you need to be over 18).