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It is not clear whether you wish to increase her weight or decrease it. Skipping is one of the best exercises. All the boxer skip to keep themselves fit. It is better you take her for swimming which is one of the best exercises. I have seen many fat persons who were swimming in the swimming pool at Campal, Panaji, Goa transformed into athletic figueres after swimming under the guidance of expert coaches of the Department of Sports and Sports Authority of India.