Workout schedule and diet plan for overweight teenage girl?

Okay, so me and my best friend have been friends for 6 years, and she's always been the overweight one. Right now, we're in 8th grade, she's 5'6" and weighs 198 pounds, and i'm 5'0" and weigh 99 pounds. I want to help her lead an active and healthy lifestyle, and she agreed that... show more Okay, so me and my best friend have been friends for 6 years, and she's always been the overweight one. Right now, we're in 8th grade, she's 5'6" and weighs 198 pounds, and i'm 5'0" and weigh 99 pounds. I want to help her lead an active and healthy lifestyle, and she agreed that she'll let me push her to lose weight and coach her, if you will, for a month and if she sees results she'll keep doing it. I really want to help her but I don't know where to start! Help? Thanks in advance.
Update: She plays volleyball, softball, and basketball, and she used to play soccer but she had knee surgery. I think she just has a problem with what she eats. Beause she's very active. Well, somewhat. Maybe she's ripped, but under a layer of fat?? I really don't know.
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