If she is trying to gain muscle, the most tried and true way is with lifting weights. There are some things that women do need to take into account to set their expectations realistically:
- Lifting weights doesn't mean you start looking like a man--that's a unique set of bodybuilders, some of whom use steroids, and not what I'm talking about.
- Women don't progress as quickly as men do. It's a physiological difference in the amount of testosterone--not anything you can do about that.
- Increasing strength will increase your muscle mass.
- You do need the support of other women who lift to work through your sticking points.
- The same plan that works for men can work for women
The community in the link I provided has a decent number of women lifters, and the group is
very respectful. Worth checking out.
A good starting program would be Starting Strength, or this newer spin on a beginner program also looks promissing: The Average F'n Program. Despite the name, it has a few good points to it:
- You have one lower body and one upper body lift each day: squat and overhead press, or deadlift and bench press.
- It's designed to keep your time in the gym no more than an hour long
- It's something that you can progress with for a good while.