My DD has hit the i won't say terrible two's as generally she is pretty good and most her tantrums were she would scream for a bit throw herself down and after a talk from either myself or DP she was fine. Now it seems she is lashing out physically at myself or DS.

Just a moment ago DS was in his rocker happily sucking on his dummy, DD who isnt allowed to have a dummy during the day unless its nap time walked over and wanted his. I said no, she kept trying to take it and i said "if you take it out of his mouth you will be in big trouble" which seemed to just provoke her and make it into a game. When i wasn't looking she took it and put it in her mouth, because she has the chicken pox he now can't use that one until i sterilise it. I took it out of her mouth, told her she was in big trouble and i would now turn cartoons off. Quick as a flash she let out her usual squeal when shes chucking a tantrum, came over to me smacked my arm, smacked the couch then walked over to DS smacked him then pulled at his clothes quite roughly (he was oblivious to the whole thing, still sound asleep) but it was quite alarming that she was that mean to him.

We use time out and smacking for discipline but both of these don't seem to be working. I have tried telling her that she has to be careful with DS as he is only little and she will hurt him but being 2 she doesn't quite understand.

So just after some advice on how to go about it as i would love to get on top of it before it escalates and i have a serious issue on my hands.