I agree the little girl is doing the steps just will extra flair. I suspect she is in her own kid logic way following the teacher's instructions to do the dance with pep or something. She also looks like in a kid logic way she is trying to pep up the others - who look overwelmed/scared.
I disagree with the they should have put her on the end idea. I think they should have put her front and center. I know at ON, Loren, Brett's recitals the confident, enthusiastic kid is often in the front and center. Their confidence tends to pep up the other kids. (Of course when they were Toddler to lower elementary that kid tended to be ON, Loren, Brett, and their first cousin those four have confidence to burn and energy to solve the world's power problems.)