T.S.
I am a huge advocate of time out. I know it seems young, but it really works as long as you use it properly (we started time outs with DS around 10 months and they continue to be effective now at 2 1/2).
Pick a spot that you don't use for anything else (ours is the corner between our front door and stairs).
When our son would hit or bite, we would say "OUCH! That hurts!" Then plop him down in the spot and say "you are on time out." Then cut off communication. In the beginning I would just stay with my back turned now, I leave the room or go on with whatever I was doing.
When the time out is over (they recommend a minute for every year, but you might start with like 30 seconds until she learns to stay there) I just go back and talk to him about his bad choice, get an appology and then go on with our day. I used to tell him "I put you on time out because you hit Mommy. I don't like hitting." but now I just ask him "Why did you get on time out." but she'll need to be pretty verbal and understand time out pretty well before you can do that.
Good luck! and I hope the hitting stops!
T.