If I see them tomorrow AIBU to calmly tell them that their bullying behaviour has been toxic, caused extreme distress, is not OK and that in years to come they will look back and feel ashamed at how they've behaved?
I'm sorry they have put her through this, and I understand completely why you would want to say something to them.
But I feel it's unlikely they will listen to you now. They are likely to laugh at you and her all over again.
If they do grow up a bit, they will come to that feeling of regret and shame in their own time. That will happen no matter what you do or say now.
If they don't mature enough to reflect on their behaviour, nothing you say will ever make them care, not now or in the future when (if) they think back to how they have treated your daughter.
Some people are immature and nasty, especially in a group setting where they find others like them and feed off each other and egg each other on. And a lot of them don't change, which is why there are threads on here about cliques in the work place or at the school gate.
But some people will eventually grow up and realise how badly they have treated other people.
I imagine they are all leaving the house and won't be returning. Hopefully she will never have to see them again.
It's not the same because it was only three days and not a year, but when I was about 23 and fairly new in the workplace, I was in a training session of approximately 30 people. One loudmouthed dickhead who must have been in his late 30's decided to make my life a misery for those three days because I was quiet and wore glasses. He would call me names like "the librarian" or the inevitable "Deirdre Barlow" and make snide remarks or volunteer me to answer questions or do the role play.
I hated him. Still do (although it's been years since I thought about him). But I did my best not to raise to it or show him he was getting to me at the time.
And at the end of the training, we were told that the exam would be marked immediately. Those who passed could leave early. Those who failed would have to stay back and complete a short 'refresher' session and do the exam again.
He was desperate to leave early (and go to the pub). He even tried to get everyone to agree to miss the lunch break so we could finish the training and get to the exam earlier, so he could leave and start his afternoon out at the pub.
He was so confident that he would pass. And then I got the highest mark in the exam, he failed, and I made sure I gave him a big smile and wave as I left first and he went back in for his refresher and second exam. Someone else I knew also had to stay back for that, and they told me that he failed the second exam as well, so would not get the qualification and would have to come back in six months to try again.
So, that's my long winded way of saying the best thing your daughter can do is rise above them, they are scum, and no matter what they go on to do, her best revenge is just being herself and going on with her Uni course, doing her best, and forgetting all about them as best she can.
It's unfair and it will probably stick with her, but after tomorrow she might never see them again, and although they might stick with her as an unhappy memory, that will fade in time and she is the better person. They have to live with themselves / each other. But the best way to deal with it now is to leave with her head held high and maintaining a dignified silence and give them nothing else to feed off.
Tell her to watch the Sarah Millican video on receiving fan mail from her school bully. That sort of payback might not ever present itself to her but who knows. In the future she might be in a position to take a little bit of satisfaction from how things turn out, even if it is just in knowing she won't ever be as shitty a person as they are.