@kathale95. I have already told her not to do it but she don't listen. Last night before this post I spanked her because she hit the baby. Lets see what happens today.

I know that with babies and kids they do a lot of stuff to see what will happen. Like my son started biting and I would tell him no biting hurts or no that's mean. I would keep it simple. But when she does hit her just tell her not to do it, that it's mean and it hurts. If she continued to do it from there, I'm not sure how you discipline (woopins, timeouts, etc.) do that. If she thinks she can't get away with it she'll keep doing it.

Idk y she's being a brat. They both get a bunch of attention.

Lol i just seen your edit. Maybe she just wants your attention. Or maybe she wants to help?

Jealousy?