S.T.
I work in a preschool and can echo that hitting is very normal at this age. One thing that can help the child is to practice other things to do with their hands. When the child is in a calm place, talk about holding her hands together when she is mad. She can practice this, and then when she is mad and you see she is about to hit, you can say just, "Hands Together!". She will get it over time. You still need to do all the other work the other poster mentioned -- talking about feelings, talking about what happened to make her hit, etc. Most important is modeling appropriate responses to anger, frustration, annoyance, etc. and giving those emotions names. Eventually she'll be able to say "Stop!" or "I need more space" or "I don't like that!". Model model model, and good luck.