Answer:
I would say that it is, D. Duchenne muscular dystrophy.
Step-by-step explanation:
It wouldn't be B or C because that has nothing to do with having weak muscles and doesn't have trouble getting up. Fibromyalgia doesn't have the symptoms as bad as this, and I believe that Fibromyalgia happens when you're more older. Duchenne Muscular Dystrophy seems like to be the correct answer, especially because she is very young, and she is having trouble walking. And also this condition happens more in girls than boys.