Diet and exercise. I also take an over the counter drug called alli to help with weight loss. It is NOT for everyone and really should NOT be taken by someone with only a few pounds to lose. I had 200 lbs. to lose (I'm halfway done!) so it's worthwhile to me.
Really, she should eat right, watch her portions and exercise, and the weight will fall in line. But SHE needs to do it, her idea, NOT with prompting. I had plenty of people prompting me my entire life, but it did not really start to happen until I decided to take control of my health.
She needs to be the one with this idea. That's the best way for it to be followed through to a successful conclusion.