I.V.
a. She is hitting to provoke your reaction, which I would see as a plea for connection, and respond to by showering her with attention BEFORE she hits, or during the times when she usually hits, such as if she hits while nursing so that you will look at her.
or
b. She may have a great deal of tension that she is trying to express. In that case, I would advise you to be very aware of preventing the hitting as described above. Try to avoid being bitten, when you can see it coming, and always respond by stopping her. But instead of being stern, along with setting the limit, try a kind voice, one that helps her feel safe enough to get in touch with whatever feelings are beneath her hitting. I suspect that if you set a clear, kind limit, looking into her eyes, she will burst into tears. Tell her "That's ok, Sweetie, cry as much as you want, I am right here" and hold her. If despite your best efforts, she does hit you, look her in the eye and say, "OUCH, you hurt me! You are mad! You can show me you're mad, but no hitting." Usually at that point your child will begin crying. A good cry will help her let those feelings out, and she won't need to hit any more.
It is also possible that she'll start giggling instead. Most parents get angry when their child starts laughing after hitting, but it is just a way of letting off the tension and upset that caused the hit. Let her laugh as much as she can. Crying may follow. In any case, after all these feelings are out, cuddle your little one and say "You needed to show me how you were feeling. You can show me by making faces. (Make an angry face here, then smile so she doesn't think you're serious.) But we don't hit."
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