My 2 cents is that you're going about this all wrong. Your girl has lots of speed and not a lot of endurance, yet you're working almost exclusively on improving her speed. For a kid like her, you need to up her mileage and get her doing solid aerobic work over the winter. What kind of mileage has she done in the past? Have her raise her previous high by 5-10 mpw and put in a progressive long run once every 7-10 days, and a 20-25:00 tempo or 25-30:00 hill session once a week. To maintain speed I'd just give her something like 5x100 @800 pace or 8x50 @400 pace, 1-2x per week all winter.
When you get 6-8 weeks out from her goal race(s), start adding in the kinds of workouts you've been talking about (2-4-2 x 8, 8x400, etc) twice a week while maintaining a long run of 75-80% the length of her winter long runs.
If this sounds crazy or off-the-wall to an interval-focused coach, I've coached a 4:49/10:23/2:16 girl and a 2:18/5:10/18:00 girl, and a 4x8 team that ran 9:33 by doing exactly this type of strength (endurance) based training.
Good luck with getting your girl some scholarship offers. Have you contacted any in-state college coaches yet and given them her running background? Those who looking for talented but unnoticed kids love runners like her with speed and a minimal endurance base, because once she gets some mileage and threshold work she could improve rapidly at the college level.