Im at the end of my rope with the kids. I need some serious discipline advice.
DD is 5, going into year 1 in Sept. She is a madam. She does not listen to a word I say. She has no manners, makes her little brother do.naughty things, answers back, shouts. You name it. im beginning to really dislike her 
If I tell her she can't do something I get told "don't tell me no!" she stamps her foot and has attitude. No punishments or sanctions work. she gets sent to her room or loses treats if I deem it necessary but it doesn't matter a jot to her. what can i do? at my lowest I've even smacked her and i don't want to end up down that road 
ds is 23mo and is learning all his naughty behavior from DD. he's starting to screech and snatch and he smacks. he's too young for naughty step byte i do try and remove him for a time out by making him sit alone on the sofa or somewhere away from toys and DD.
im just at my wits end.
DD used to.be so good and polite. the last 6 months have been awful though.
please help me 