Question

why was zitkala upset when her long hair was to be cut?

Answer 1

because she liked her hair long and she was upset when it had to be cut.

Answer 2

It was an age old tradition among the people of tribe, to which Zitkala-Sa belongs, to maintain their long shining and beautiful hair. It was believed that only the warriors or the mourners get their hair shingled. Short hair worn by the cowards as per their tradition. So, obviously Zitkala-Sa never wanted her hair to be cut short.