Explain how loosing weight so fast will lead to a rebound later. After the wedding is over and she starts easing of the diet and training, the weight will come back with a vengeance. Losing that much in a couple months is nearly impossible, and if a large amount of weight is lost in a short time, the body receives it as a signal of starvation, and it will react by slowing down metabolism and holding on to fat. I would recommend either postponing the wedding until goal weight is achieved slowly, or coming to terms that she won’t be able to be 69 pounds lighter for it and realizing that the wedding can just be the beginning of her journey, not the end all! Hope this helps and good luck!