What are some good dieting stuff for 11-13 year old girls?

I take care of my Little sister but I have only been taking care of her for a few mountes and shes an allstar cheerleader and the coach sayed she needs to be put on a diet but I want her to stay health and strong and I dont want to take all the food out of the house she has to lose 5 pounds in the next 2 mountes before her comp. douse eny body have eny Ideas it would help so much thanks guys