How to discipline a child (becoming difficult)

I know slapping is a no no .. but I get so annoyed with ther fits, my ammi never hit us and I don’t want to be a bad mommy but don’t want her to take advantage of my goodness, can you understand what I mean. sigh

Its hard to say lets stick to a routine, she loves going to her kindergarden (nursary) but sometimes will not brush her teeth or goto the toilet when its time for bed, I tell her if you dont then we will not go to KG tomorrow, this works sometimes and sometimes it doesnt.

Take away her favorite activity (toy) she will cry till I give in and she is very stubborn she WILL cry till I give in!

We do have a set of boundaries but lately she is calling me stuff like stupid cat, I think she has learned a new word in KG.

The thing is maybe she is jealous that I am giving time to the baby, but I have to feed her and look after her as I did to her when she was small.

Don’t know its so hard, I have tried different methods but when its gotta be her way it gotta be her way!