Which is are some great meal and exercise plans for a 12 yr. old girl?

Glad you ask: Happy to see you are motivated to eat and exercise well. The best answer is for you to have a one to one session with a nutritionist who can help; you with the meal plans and perhaps a session with a trainer to help you design a plan for you. Best exercise plan is one you like, vary it, and do not stress about it. Walking, climbing stairs, mild weight lifting can all be beneficial, .