This was my DS a year ago. He was actually more extreme because he would do really dangerous things like trying to push over his bookshelf. We screwed the furniture to the wall but he'd dangle on it with all his weight, it was horrendous. And he'd attack us. It was very confusing because he was actually very well behaved at every other time.
Three things helped- loads and loads of quality time together during the day, getting ready for bed quite early with a break between getting ready and actual bedtime, and not giving the bad behaviour any attention. I know some might disagree with totally ignoring the bad behaviour and say that we should have talked about feelings/supported him through it, but that didn't work with him (he HATED me doing things like naming his feelings etc) and he would instantly ramp it up.
Firstly, I recommend getting washed/teeth brushed/into pyjamas BEFORE a calm pre-bed activity like colouring or Lego to take the friction out of the getting ready bit. If you explain that after getting ready for bed you will do xyz together, she's probably less likely to be resistant.
In my DS's case, the behaviour was essentially down to FOMO (a while after it got sorted out, we were chatting about how bedtime was so much better and he said it was because he would far rather be doing things downstairs with me and knowing that daddy got to stay up and spend more time with me made him cross). From his point of view, the bad behaviour was actually very effective because it kept me upstairs for ages dealing with it. But that may not be the case with your DD.
What worked for this aspect of the problem was lots and lots of time after school doing things together. While we had plenty of quality time together anyway, I really made a point of making sure we had 1:1 time crafting, gardening etc every day.
When the behaviour started, I did my absolute best not to comment on it and would just go and stand outside his room with the door shut. I'd say something like 'I'm going to stay outside until you've calmed down because I need to keep myself safe' (if he was hitting/chucking stuff about) or 'the screaming is hurting my ears, I'll come back when you're ready to use a calm voice' etc etc. It very quickly stopped when the bad behaviour achieved the opposite of his goal (as in, I stopped being his audience). I can see that the screaming is upsetting for her sibling but you may need to ride it out a bit.
Consequences like cancelling treats etc never worked for us- it's too long after the event and the connection between bad bedtime and treat is too abstract.
This is what worked for my DS, but different children need different approaches. But I really hope you find a solution soon OP, I know how exhausting it is 😩