I know a kid my daughter's age who has been flying by herself for years. She was champing at the bit to fly as an adult, rather than an Unaccompanied Minor. My daughter has barely flown at all, so she had almost no experience with airports at all. I remember the first time I flew by myself, I was about 25, and I'd hadn't flown much either, and I was pretty scared. It wasn't that I didn't think she could do it by herself so much as I was pretty sure she'd panic very easily if she didn't find the gate right away. That's why I kept her on the phone with me. I mostly just listened as she told me "Oh, here's a sign--nope, not that way". I was panic prevention more than guidance.
That said, the experience was possibly more stressful for her parents than it was for her. It was her choice to fly alone, we made sure she felt like she could handle it before making the travel arrangements. Back then she was excited and as it got closer she was getting cold feet.
I think she'll change a lot during her two weeks away. She's got a shy & insecure streak that is typical of girls her age and my sister & I both outgrew it. I'd be surprised if she doesn't gain a lot of confidence this summer.
2009 Trek 7.2FX WSD, brooks Champion Flyer S, commuter bike