this situation also happen on my son, he's near 18 months.
my suggestion is: let her try and do herself, don't help her anytime, since she's more than 2 years, if she angry about you don't let her use chopstick then put it on the floor, its acceptable, if not, you should told her "NO, you don't do this" and told her why. I believe that she understands what you mean at this age.