Tips for my friend, Losing weight?

My friend wants to lose weight. She is 13 and she weighs 61 kgs. She is 5"2. She want to weigh 48 by the end of May. Any tips for her?She doesn't like running. She likes riding her bike and going on the trampoline. She also would like to know- How long should she jump on the trampoline and ride her bike for? and also could you please give her a calories site thingy. Cos she can't find any good ones.