Oh she'll be fine! I think these sort of things are very important for children to learn a bit of independance. When I was 8 I went away to Canada ski-ing with my school, did disneyland at 19 and an adventure holiday at 10. I think it really helped me 'grow up'
My dsis who is now 18 went away on a trip through Europe with her prep school at 9, staying in a hotel room with another 9 year old and an 8 year old, as the hotel had buggered up the bookings they ended up in a room on their own on a separate floor from anyone else in their party, my sister couldn't even reach the shower to turn it on (she is a midget though) and they ended up having a great time with room service!
Important lessons will be learnt but it is best to learn them when there is 3 or 4 responsible adults there than when you are backpacking across themongolian jungles on your own... (ie don't throw your backpack, inside of which is your passport, all your money and your plane ticket to another boat when you row into a fountain 'to stop it getting wet' as chances are it'll get much wetter when it doesn't make it to the other boat - not me I hasten to add!)