Those of you who would immediately collect your children as soon as they said they found the situation difficult - you do realise the damage you are doing them, by teaching them to immediately give up as soon as they face challenges, and that any negative emotions they have are an emergency and a disaster that must immediately be fled from?
It seems a somewhat selfish, cruel and lazy approach to parenting, rather than taking the (admittedly more challenging) route of supporting them to actually overcome their problems, rather than running from them..
OP, unless you think your daughter is at risk of harming herself or others, please don't rush to collect her immediately - you would be totally undermining her resilience if you do so.
Look at the reasons she has given for her unhappiness - that others aren't hanging out with her, and there isn't much to do - it's hardly an emergency situation, is it?.Honestly, if you teach her that it's not possible for her to sit with these emotions, you will do her untold damage kn the future.
Do speak to the adults running the camp, as it may be that they can put things in place to support her. And above all, help her to get this in perspective. She's feeling a bit bored and a bit left out - she's strong enough to cope with that, if you remind her that she is!