Quickest & Safest Way To Lose Weight? [14-year old Teenage Girl]?

My little sister really wants to lose weight. She weighs 135ish pounds at 14 years old. She doesn't have the time to go to the gym and do a workout. She wants to lose (mainly) her belly and thigh fat. She says her goals are 5-10pounds each week. She plans to be 115 by the end of April. I know it seems extreme. Her metabolism is quicer though because ofher age. So any methods on how she can lose weight by reaching the goas of losing 5-10pounds weekly?? Any advice & support is welcome.
Quickest & Safest Way To Lose Weight? [14-year old Teenage Girl]?
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