Our school do a voluntary trip at this age, quite a few go, but there are a significant number who don't either because their parents think they are too young, or because they themselves are not ready.
A previous (small village) school used to take the whole of KS2 away every 3 years, so some went when they were in year 3 and some in year 6.
When I first read your OP I was in the 'encourage her to go' camp.
But as she can't even manage staying over at grandparents yet, I would say she definitely isn't ready.
Don't go to the same place the same week. If you want to, take her there at some other time.
Go in and talk to the teacher, be clear that as she cannot even manage one night with grandparents, there is no way she is goign to manage this trip.
Ask if there is any way you can support what they are doing while they are away. eg if they do pond dipping, can you find a way of doing that, using on-line info etc.
Can you do a mini project on the area, so if it is all about fossil beaches, you have found out about and looked at all the same things school is looking at.
I would ask school seriously what she will do while you are away.
A pp said they had to sit isolated in class etc ect. I cannot imagine any school I know doing that today.
In fact, it may be that she has a special week. We have had older kids who become the 'helper' in reception for a few days when this happens and they get a bit of responsibility and a bit spoilt by the reception teacher who feels sorry for them. So staying in school may not be a negative experience.