Since our DD is an only child, she has been taking a friend with us on vacation since she was about 10. The first few years is was the friend de jour, and usually worked out well. We made sure the parents had all our contact info and that we had a notarized letter from them allowing us to authorize medical treatment for thier child in case of emergency along with thier insurance information. The parents usually sent spending $$ for their child (except in one case) and we picked up the tab for everything else unless airfare was involved.
During her high school years, dd took the same friend each trip. Heather was considered one of the family so it was no problem having her with us. We're DVC members, so when vacation was a trip to Disney, we always got a 2 bedroom so the girls could have their own space (really it was so DH and I could). While at Disney, the girls could do their own thing as long as they checked in with us at pre-determined times. They usually spent the days at the parks with us and then went out on their own after dinner. One rule was they always had to meet us for dinner somewhere. They had to be back to the villa by 11PM. When they graduated from HS, we took them both on the Eastern 7 day cruise and we all had a blast.! The girls are now roommates @ Penn State and will be joining us in Nov. at WDW. They will be 19 and 20 so in honor of their "grown-up" status, we have reserved them a studio @ SSR by themselves while DH and I stay @ VWL.
I'm sure your DD will have a wonderful time and so will her friend!
