What to do?

I have a 21/2 old daughter. She is very well behaved some time but when ever she becomes ill mannered i tell her to stop doing it so she ays it back to me, i tell her to be quiet she says me to be quiet , i tell her that i will lock you in the room she says it back and then she gets a slap. After while she says sorry to me an d kisses me but agian the whole process starts after half hour or so. I think that it has become like a routine for her she also hits back to me if i do so. Please give me advise what to do in such situation. Beside this she also eats toothpaste while brushing her teeth and this thing make me mad too. Please help me out. Thanks