6yo completely loses the plot after TV/tablet use, what do I do?

Very much agree with this. Op stop tv during the week and see what happens. I think you’ll see a big improvement for her. Help her in that way rather than use screens.

it's like the content/the screen itself does something to her brain.

BINGO

We know this. You could do a quick half an hour research on the effects of screen time on the brains of young children and learn a lot. This is exactly what is happening.

She's drawing her sister a picture because she feels guilty? That's not a good thing. She shouldn't have been put in this position in the first place. She's a six year old, you are the adult, you're placing far too much responsibility for this on her, it's you that needs to wake up to what is going on here and help her, not punish her.

100% agree movies are the way forward but you don’t need to do all the faff with DVDs and a PC. Just delete everything off the tablet that isn’t Netflix or Disney Plus (whatever you subscribe to) and download some chosen films in advance. Then so long as the tablet isn’t connected to the internet whilst travelling then that’s all they will be able to watch.

What we've done for long distance travel, is burn a few Disney films from DVD onto our PC, and then put them onto the tablet, so the kids can watch a film if they're getting restless towards the end of a long journey etc. I've found that actual films are SO MUCH LESS over-stimulating than anything else that's on a tablet (shorter videos, games etc.)

I know a lot of people don't own films on DVD anymore, but you can pick up a few dead cheap from car boot sales, charity shops etc. or even the library I think.

OP - you are the only one who caused this. It’s up to you to cure it. You gave her the screens, it’s damaging her so take it away. No judgement - everyone is doing it and thinks it’s fine. Total judgement if you don’t take the good advice given to you on here.

Youtube is absolutely awful, I have to constantly be on there blocking 1000s of channels that make my DC go absolutely loopy. I have a recurring alarm set to redo this every 6 weeks as the worst offenders seem to create new channels all the time which come back on. I should just get rid of it TBH but there is stuff they watch on there they can't get anywhere else and it would cause WW3 but I wish I had never let them on it in the first place, it's complete nonsense.

I can spot the prime offenders a mile off now, I think they are AI generated a lot of the time, it's all weird sound effects, gigantic eyes and repetitive high stimulation graphics. And the plethora of strange families jumping around in completely white made up houses. Bizarre.

‘So 6, I’ve noticed that when you come off of screens your behaviour changes, have you noticed that?’
’ it’s not acceptable to hurt your sister or me, so for now, the consequences of this behaviour is to not have screens. We’ll try again in a week and see how it goes.’

she needs to understand consequences. If you find this with ending or changing other activities, then she might need some help with managing transitions.

Stop all screens including TV and it’ll probably help.

Get rid of the screens..

Sweden is now stopping them in school too.

She is not grown up right now. That’s what counts. She doesn’t need to do at six what she might do at sixteen.

The majority of comments mean limits and warnings for tv, the iPad needs to go full stop.

Is this child watching youtube by any chance? If so, I would remove access to this via tv and ban the tablet.

At six, mine were allowed CBeebies, Milkshake and the odd Julia Donaldson thing on telly. That's all they need at that age.

but it's like the content/the screen itself does something to her brain.

No, people get it. That’s why they’re telling you 6 is far too young to be sat on an iPad.

Just no screens.
If she's reacting in this way then the best thing you can do for her is remove them entirely.
TV is not the same as it was when we were growing up, its designed to be addictive now and its not good for them especially at a young age.
Some people will be able to give their kids screen time without issues, other kids are more sensitive. Just because it works for someone else doesn't mean its worth doing for your child.
We have our TV in the dining room now with a blanket over and we only bring it into the living room/playroom for a family movie once a month ish. No other screens in the house available to our kids and our 4 year old wasn't having anywhere near the level of reaction as your child. We just felt she was getting obsessive and overly upset about it being taken away. The more she got, the more she wanted. (We actually weren't doing much tv time anyway but when my youngest was born and had colic we were not coping and fell into the trap)
Also netflix kids has an extremely wide range of shows available, many of which are not suitable for a 6 year old.
I read an interesting study that the smaller the screen the more focused the child is on it and the higher the likelihood of issues like this. So TV in the corner of the room is much better for them than an ipad or phone right in front of them.
In terms of long distance travel - we actually really struggle with our daughters behaviour after long haul flights because you can't avoid the screen and you don't want a meltdown on the plane but then she's nuts for a few days afterwards, desperate for more screentime.

I can’t speak for others but I understood your original post. There is a chemical reaction that takes place in people’s brains when exposed to screen time, and it’s much more impactful with short form/instant reward content such as YouTube and some Netflix shows. It’s a dopamine hit, so although she may come off the screen fine, there is so doubt that the effects will linger and cause difficult behaviours.

I’ve seen it with my own, and we stripped everything right back. Of course, a lot of it is just kids being kids, but there is also a lot of science behind the impact screen led lives can have, particularly on developing brains. Not saying this to patronise etc, but it’s stuff I’ve discovered through similar issues a couple of years ago.

Hard to avoid screen time but I always try and give warning and ease the transition before turning off. Would also recommend Yoto player and/or Tonie box for screen-free time they can listen to stories

Absolutely no tablet use. If she’s using one at school, thats a reason not to at home. Use a timer for ending tv time. If she tantrums then no tv the next day.

And also yes to all of this!

We have total YT ban now on all devices. It's absolute mind numbingly shite content that for some reason the kids are hooked on.

At 6yrs old they really wont be needing to use screens constantly at school. It is as simple as massively restricting screen time at home, as they're showing they are unable to cope with the transition of it ending. Find other things that seem equally exciting or spike their curiosity instead.

I have 2 DCs, my youngest is 5 and would happily sit on screens all day and forget to eat or drink - he just seems unable to regulate it himself at all and finds it addictive. Eldest is 10yrs and isn't built that way and gets bored of screens naturally after about 20mins (tablet, switch, TV... he just isn't too bothered). Some kids just can't cope with screens and do need really consistent and firm boundaries. I tend to leave a big basket of random toys in the middle of the room and wait for the kids to get curious and dive in - it makes turning off the screens less intense as its essentially redirecting their attention.