@nooboo2 - When you speak to your DD in the morning, if she's showing any positive signs that she might want to stay, I would encourage her to think of the following:
Yes, all these children go to the same school - a school she will not be attending, BUT they all live in the local area. People don't only socialise with friends from school or college; teenagers often have other friends too! Some may be friendships formed due to them being close neighbours, they might have Saturday jobs at the same place, they could have met at a party and hit it off, they may have friends they know from a group, such as Guides or a Drama Club, their parents might be friends and they could have met through them, they could have gone to infant school together but been separated for Middle/Junior school, but then gone to the same Senior school - or they could even have met on a 4 day summer holiday activity holiday, 2 hours from home!
Teenagers don't only socialise at school either, so any friends she makes on this activity holiday are likely to want to meet up with her to go to the cinema, to parties, bowling - or whatever it is that teenagers do when they get together after school or at the weekends these days! (my DDs are only 10 & 12 and it’s 20 years since I was a teenager!) It would be lovely for her to have some new friends to hang out with over the summer, and it's probable that some of them will know girls at her new College who they will be able to introduce her to when they get back, so she can begin to make friends who go to the same College as her before she starts in September.
I think if you can get this across to her, it might be enough 'food for thought' to help her to see the positives in sticking it out.
If, despite all this, she is still upset and wants to come home, I would go and get her - I wouldn't be able to bear the thought of one of my DDs being away and wanting, desperately to come home - to the point of sobbing down the phone but me forcing her to stay there and stick it out. It would leave her feeling utterly powerless and would be likely to adversely affect your relationship with your DD for some time to come, and coming so hot on the heels of her parents deciding to move her away from her home and friends, that could be disastrous.
If you do end up taking her home today, I would ask her to sit in the back of the car with you, so you can talk. I would start off by apologising for hanging up on her, as that was very rude. I would calmly explain again the reason why DH couldn't collect her last night, as she may not have been in a fit state to take it in when she was so distraught when you spoke last night. Hopefully she will apologise and thank you both for coming to get her and will have calmed down by this stage. I think then would be a good time to talk about how she's feeling after the move.
We did a 'big move' when our DDs were 8 and 10 and we spent a lot of time before we left talking about all the changes that would be happening and how they felt about them and coming up with various coping mechanisms, but once we had moved, I made the mistake of not following up and finding out how they were really feeling post-move. Obviously I asked how school was, were they making friends etc. but I didn't really give them the opportunity to just tell me what they wanted to tell me - of course I listened when they spoke to me, but what I mean is I never explicitly asked them "Now we've moved to ‘New City', how are you feeling about it? What do you like more here? What did you prefer about 'Old Village'? What could DH and I be doing that would make that easier/better for you?" etc. I have a feeling that your DD might appreciate the opportunity to get it all off her chest. It might be an emotional conversation (bring tissues!), and I'm sure she'll leave you with a healthy dose of 'Mum guilt', but in the long run, teenagers really appreciate being listened to, and feeling that she can talk to you about this stuff, that you are interested in how she feels about it and that you want to help, may well strengthen your relationship.
Oh, and do not mention all the money you spent on stuff for her trip - she'll probably use most of it at some stage anyway, and you're trying to make her feel better, not worse!
Good luck, I really hope for your DDs sake that she chooses to stay, but if she still wants to come home, have a safe trip.