The trouble is, it's not as easy as 'just swap them round a bit'.
Year 6 girls usually team up in pairs & want to share with a bff, & staff will usually let two friends share as they'll both be happy, have a mate if homesick, etc.
That means you then have to put them in 4s & sometimes those groups are obvious, & sometimes you have 'well Anna & Bobbi will have to go in with Charlotte & Dima, they're the only two pairs left'. (Or indeed 'we can't possibly put Anna in with Emily, she'll be foul to her. Charlotte & Dima won't stand for her crap')
& sometimes you have one less than ideal room made up of 4 kids none of whom would necessarily have chosen each other.
& then it's a couple of weeks until the trip, & all the kids are buzzing & looking forward to sharing, & suddenly a teacher who did the rooming is finding out that your dd & bully have bad blood the teacher didn't know about.
About all you can do then as a teacher is choose a nice kind foursome with sensible parents, & tell them 'you two are in with {OP's dd} & you two are in with {bully}.
The girls won't like it. They will go home & moan. Their parents will phone up & complain furiously. & as a teacher, you really can't exactly tell the girls or their parents 'yeah, we've broken up your happy little friendship group BECAUSE you're nice kids who will be kind & suck it up'. Nor can you obviously pass on confidential information about the bullying.
Yes, it's shit. It was my dd 2 years ago (we got it sorted - mostly because one of the other mums is a good friend of mine, who had a quiet chat with her nice dd & got her & her mates to swap round & include mine) - but honestly at this point, appeasing you will piss off several other people.
Your best bet is to be the one who will get the most mediaeval on their arses at this point! Definitely talk about 'safeguarding' & 'duty of care' a lot.
Bloody useless of the school not to spot this much, much earlier.