My 4 year old has developed a big attitude?

hi my child in the last 3/4months has just been out of control she talks back to me shouts at me and never dose as shes told i feel like i would be better talking to the wall, i have started given her a warning then after that when she dosent listen i put her PJ's on and put her to bed and that's her for the night i dont give in to her but its not working and im getting very run down and dont no what else to do any advice would be great! oh also theres been no change in the house that would upset her routine at all.