Keep in mind, many 18 yr old girls head off to college, often out of state from their homes. Some join the "Greek System", and suddenly have a tremendous amount of contact with other boys or young men, as well as access to alcohol, and what not.
The OP is just 2 years younger than that, but already taking some college courses. Is she headed into early college admission?
Lots of good suggestions though.
If it was me, I'd probably use the 2016 summer as a prep year. Go on a few cycle camping trips, mini tours, etc. Keep within maybe 300 miles from home.
Then, either work or study during the winter of 2016, and start the grand tour in spring of 2017. It may seem like a whole year wasted, but it wouldn't be wasted. I'm sure there are a lot of interesting things to explore near home, as well as a lot to learn about striding out on one's own.
Good points about learning to be self sufficient. Get 1000 miles from home, and Mom & Dad won't come to fix a flat tire or splice a chain. If the OP isn't familiar with her bike, then hang out at the local bike co-op, or take some bike maintenance courses. Maybe try a scratch-build of the ultimate GIRLY touring bike.