Some suggestions:
Typing. Make her take a typing class to get her WPM > 60.
Math. Find a math curriculum that will take her >= Calculus and DFFEQ. Use this to supplement what she gets in school. If she spends 3 hours a week on this during the school year and then works at it 6 hours a week in summer, she will do very well. If she likes proofs in geometery, then branch out to logic, analysis, and number theory.
Computers. A basic programming class in C followed by a class in numerical methods. Find a community college for this. This will teach her how to use applied math. Knowing how to build algorithms, test them, then write them is key.
English: Find a reading group at your local bookstore that gets together weekly to discuss a book. This is great fun for a young kid.
A technical hobby of some sort would be good. I'm sure she'll come up with something. My DW did Ham radios and RC airplanes when she was in HS.
Latin is good and so is Greek. The history you learn is just as good as the language exposure.
