My 9 year old daughter is being picked on?

I have a 9 year old wonderfully pretty daughter. I checked her myspace account only to find in her mail that kids are picking on her. She is not the thinnest girl in gl but not overly on heavy side. She has put on some weight in the stomach area, the kids have noticed and are calling her fat, saying she needs better clothes , and she needs to spell better. I don't know where to even begin, i cant have my daughter be the kid picked on! it hurts so much to know this and to find out through her myspace account. any advice please! she also begged me to put highlights in her hair the weekend so i did, after reading those messages it just makes me wonder if she wanted them to please the kids or hoping if they didnt like them it would draw away the attetion on her weight. ????????????????