In my house screen time began at 5pm. Any bad behaviour was met with a correction, and if necessary a warning. Then they lost 5 minutes of screen time. 10 if they wanted to keep pushing. By that I mean the start time moved to 5:05, 5:10.
If we got to 5:15 we probably had a bigger problem, and I’d stop engaging while I thought it through but that was very rare.
so to take one of your examples
she was eating a sweet that’s someone at school gave her as it was their birthday and I said it smells nice and she said that’s because it is nice stupid why do you think I’m eating it.
I’d say, “oh? It’s not ok to speak to me like that. Let’s try that again: yes it is a nice sweet mum. Or maybe you could tell me what flavour it is”. (Mild correction)
If she repeated one of those phrases, said something else acceptable or just fell silent for a while, I’d consider that reasonable.
If she insulted me again, I’d say, “you’re going to lose 5 minutes of screen time if you don’t speak to me nicely” and this time I’d expect her to either rephrase or apologise and subside.
If she fell into line, I’d just happily engage as normal, and consider the matter over.
If she didn’t, I would stop talking. Don’t say “well now you’ve lost screen time etc” as that’s just engaging with poor behaviour and adding fuel to the fire.
But if she escalates, I’d say “do you want to make then minutes?” (Warning and another opportunity for her to take the exit) and if she continued that would be ten minutes.
It is absolutely vital to put the time restriction at the beginning of the next screen session. It’s far easier to enforce than at the end, because she will want to get the rest of her session. Don’t take more than 15 minutes or take the entire amount of time or you’ve lost your power. Small, consistent penalties are much more effective.
In my house I included an option to do a chore and earn back the 5 minutes (which helped avoid whining and begging or another explosion when 5pm rolled round. I would let them empty the rubbish, fold some laundry, pair socks, hoover one room (something relatively quick that would only take a minute or two)
I was dealing with an autistic ds who was dysregulated by school, had a pda profile and this method worked brilliantly. I never got angry, or loud, but held the line both in terms of his behaviour and as a calm presence.
It may be the case that you need to adjust your expectations a bit - my ds needed some decompressing time after school and wouldn’t have handled questions or a conversation with me on the way home. (We had a version of the above where the substituted phrase was “I’d rather not talk just now mum”)
He's a calm, responsible and very pleasant teen now so this does work.