To cancel DD’s dance comp after what she said to her little brother?

Give her an alternative punishment , anything you can take from her , iPad , iPhone ? Warn her you are taking it a few days and if she keeps her behaviour it will be an extra day for each time .

Kids spill things, if it's an accident then it's a shame.. Siblings call each other names, that's also a shame. Both things are normal family activities! DS should be made to apologise for not being more careful when near his sister's clothes, DD should be made to apologise for calling DS a rude name. Cancelling the dance competition is way over the top and seems to be due to the fact that DD already had tears in his eyes, bless him - at that age they can summon tears magically at any given moment, it's a response to the shock of maybe getting told off for the accident. At no stage do you suggest he should apologise but you double down on her straight away.
If the age difference were greater, IE if she were 16 and he was 3 it would be a different scenario but you need to remember that she is starting puberty with all the hormonal imbalances that brings and does not have the emotional maturity to handle something that in her eyes is the end of the world!
I really hope she was allowed to go to the competition and did well in it. Afterwards you can tell her how upset her words made you and that you expect her and her brother to be courteous to each other. If the competition is cancelled for something she will perceive as his fault, you are going to have a lifetime of resentment and family upsets to deal with.

Depends on the accident?

A genuine accident, you tell them off, because accidents or not, they have consequences and they need to learn.

An accident waiting to happen after you told them many times to stop messing around, or not to take a drink somewhere and to be careful? Yes, you do something.

Just looking at the posts from the OP, sounds like her DD would be punished, but not her son.

It’s clear who the favourite is isn’t it?
“little one” 🙄 he’s 8. No wonder she was pissed off. I get the impression she’s sick of her feelings being bottom of the priorities list.

Hope the 8 year old was “spoken to” as well but I doubt it

FGS, the apology would be enough! Don't go looking for another punishment on top.
Have a chat with her about her brother's condition at another time and let her know you understand the impact on her. Reassure her but make it clear such slurs are not acceptable.

Blimey, people on here have been very harsh. Yes you did overreact but we've all been there. I have 2 daughters 15 & 13 who are utterly hideous to eachother at times & I'm horrified that they can be so vile. But I remember back to friends & their siblings when I was a kid & they were all pretty nasty at times. I'm an only child so don't understand the need to be such an arsehole.
All people spill drinks, even adults. Hopefully the top can be rescued.
As for people being outraged at you describing your daughter as "banging on" about the comp join the real world. Kids/teens do get mega excited about this stuff to the point it's the centre of their life but, life goes on & it can be rather trying when they "bang on", especially when we are tired or have other priorities/worries.
Put it down to a bad day & hopefully she went to the comp & smashed it.

I think a talk with them both, explain to each why they need to apologise, your son for being careless and causing the spill on your daughters item and explain to your daughter that she should apologise for what she said to her brother. She may have over reacted but it was caused by your ds carelessness and she had her top possible ruined then to punish the one who was the recipient of your ds carelessness is very harsh. I think apologise all round and let her go.

I hope you are still reading all of the replies OP for the sake of your whole family.
I do actually get what you are trying to achieve and I do have a very good friend who once really shouted at her older child in-front of me because she said something very similar to her younger SEN sibling (ages very similar to your scenario). The difference is that my friend invested a great deal of time in both her children equally and so obviously loved hearing about their ambitions, hobbies, hopes and fears. When she shouted it was in a controlled manner, apologies were made by both children and then it was forgotten because the message had been received loud and clear and expectations were set for both children. She is a highly trained teacher though!
If it helps, the elder child is now thriving at Uni and the younger doing well at a Special School and they get on well and clearly love each other.
I respectfully think you need to actually be the parent more, so providing a good example to follow, rather than blowing up and over punishing then expecting the children to get along and your eldest not to resent the way you have handled the situation.
The way you speak about your two very young children is really a bit sad; you risk alienating the eldest and infantilising and potentially hampering the development of your youngest.
Happy homes are not those which avoid arguments and tears, but more ones that can deal with them in the moment and then teach a better way to communicate for next time.

Let her go, she sounds excited and stressed. I would just ask the chidren to apologise.

Wow, that was a mild insult for us as kids. But I love my brothers and wouldn't have meant it, it's just hard sometimes being a kid with big emotions and so little power over your circumstances. I'd try and get a little more tolerant OP before teenage years arrive. Kids say a LOT of stuff they don't truly mean.

You’re insane. DD did nothing wrong. 8 year old mummy’s favourite DS spilled juice all over her top, probably on purpose.

I would grow to hate a mother like this.

Massively over the top. And you may as well have told your daughter that her brother will always come first. Poor child.

You would punish a child for an accidental spill? What is wrong with you?

Perhaps your DD’s attitude stems from your favouritism and the difference in treatment each of your kids receive? Read how you described each of your children. She was “banging on about” “INSISTED she had to have” versus, he’s a “little one” and “bless him”. If this is the tip of the iceberg, you may have created her resentment of her brother, which is only going to get worse if you punish her this severely. It may not have warranted punishment for the brother (accidents happen after all), but he’s spilling drinks and balling about it at 8yrs old and getting coddled, while your DD’s reaction was understandable given how important this is to her and that, ya know, she’s still a child too. They just need to apologise to each other and not have parents who play favourites.

are you on a wind-up or have you not even read the OP?

I believe she was saying this is what SHOULD happen, not what did happen.

Her attitude is intolerable and you will be making a 'rod for your back' if you let her get away with it.

If she is that strung up, perhaps the dance competition is not for her yet, and wait a while.

Have a little word with her when she is a little calmer. Tell her that accidents happen at all times, and try to get the stain out and show her that something good can be redeemed out of every disaster. Every disaster is a lesson to learn for the future.

Not too many sparklers though. It might not be safe if one falls off in a dance and she steps on it.

I broke a cup in my kitchen. Do I need to be punished?
Dd's show should not have been and isn't cancelled and yes dd acted in nerves and frustration but this boy doesn't need to be read the riot act either, accidents happen in life and he was remorseful immediately.

How did the competition go?

Whats DSs punishment?

Dd needs to apologise and understand she's responsible for her reactions regardless of her feelings. What she said was nasty and it isnt cool to be mean on purpose because someone hurt you accidnetly. But DS was careless and inconsiderate

Let her go to the competition. Her nerves are obviously strung tight. Preventing her from going will not improve things with her brother or you.

Competition depends on a genuine apology and an effort towards amends.

But if she said sorry properly I'd let her go after a discussion about kindness

It’s so clear from your post that you favour your son and resent your daughter, I feel sorry for her

It's a natural reaction if something you have been focused on ruined. You completely over reacted. people who are not a toddler's mother do not find this kind of incident adorable .You need to back down as gracefully as possible .I've just checked, he's 8 ,he should have been more careful -and you should not favour him so much, it is really unfair .