I started with my fingers when I was young. It then led to my back and neck. That's about it. Sometimes my hips pop if I stretch them, or knees crack if I squat for an extended period of time then stand up, but nothing out of the ordinary. She may grow out of it.
Cracking joints is actually good for the joints. It pops the air bubbles which is what makes the noise and streches the ligaments like you would a muscles. And being able to pop more than just your knuckles is normal.