They both are making mistake by opting only one thing of their choice. One is willing to cut her calories while other is willing to do more physical activity. Whereas it should have like the combination of both for losing weight for good. They must cut some calories or opt healthy food choices along with some physical cardiovascular activity and some weight training to tone their bodies.
Losing weight is not about losing weight for a period of time by making some changes for the time being, rather weight loss is a change of life style that involves healthy eating plus regular physical activities. So if they want to lose weight, they have to go for both.