Could your DD do one worksheet the teacher's way and write a description of how the teacher's method works to prove that she understands it? If your DD can also explain how her own method works and why it gives the same result that would be even better. Maybe that could convince the teacher to allow your DD to use a different method.
A lot depends on the teacher... some teachers would perceive this as "showing off". I know, because I was a talented math student who ran afoul of some of my teachers
