These 4 year olds were sent to test us 🤯 mine was screaming in my face the other day so I told her I wasn’t going to listen to her until she stopped screaming and she shouted “I’ll stop screaming when you give me what I want!” I just kept calm (big struggle) and reiterated I would not listen to her while she was screaming but when she is ready to speak properly I will be there to listen. I stayed in the room with her and she came and sat beside me until she’d calmed down. No idea if this is the best approach but it worked that time!
Similar to what @Katrina said, you need to remain calm, redirect and remind. So when my daughter who is now 5 may say “I want a chocolate bar NOW!” first of all I say to her “those who want, do not get. How can we change your question to ask nicely?” and then she’ll think for a second and say “Can I have a chocolate bar please mummy” and then the answer will either be “that’s much better. Yes you can go get one from the cupboard” or “sorry baby, it’s too close to your dinner time, you’ll have to wait until after”. The time when she is lost in repeating the “I want a chocolate bar NOW” loud phase, I remind her to use her indoor voice, reiterate above about asking question differently and then come find me when she has remembered her manners. I’ll stay in the room doing something else, it doesn’t usually take her long to stop sulking, calm down and then find me.
As for your daughter saying “if I want something you have to get it for me” you need to nip that idea in the bud immediately. “No baby, I am not your servant. I am your mummy and I decide what to give you. Just because you want (insert X) doesn’t mean if you keep shouting louder that you’ll get it”. If she goes to nursery or pre-school she may have watched another child say/do it and got their way and picked it up from that. Or TV. Peppa Pig is awful for this. At 4, it’s all about power play. Where possible, try and give alternative choices. So if say she demands something for dinner, you can give her a choice of X or Y instead.
When my 5 year old tells me or dad she wants something we always respond jokingly we want a million bucks or something silly... when she says she doesn't have money or that much we respond we don't always get what we want and what should you say? (I do have a look where she corrects herself now and turns want to please)
I would say that's an interesting idea, where did that idea come from? There are lots of ways to get the thing that you want. One way would be for me to get it for you now, another way would be for you to get it yourself, another way might be for you to help me with something then I get it for you, you could ask your dad/brother/grandma, these are all possible things that could happen..... if getting it for her now doesn't work for you, or you need to finish something first, it's ok to be honest and say that. I often give my kids a list of the next three things I'm going to do during the day. 🙂
Maybe acknowledge that you hear she wants X, and then tell her something she can have?