don't worry so much - your daughter will have plenty of people to keep an eye on her within a few days of being on the trail..
Taking a light weight tent will give her sleeping options if she's not comfortable in the shelters, due to scurrying little feet more than crazed fellas...
Nothing wrong with condoms, they're a sensible option , truth is that most people stink so bad on the trail that there is very little sex going on without mutual consent!!
Good luck to her!