So yes flat road running will help your uphill travel in the long run to a point. Particularly with building some aerobic base. I live in a mountain town and still do alot of road running while the snow melts in the hills (still snowing actually). Supplement with 1-2 leg strength session (Chamonix Fit is the shit). After you build her base well you can have a period of 4 weeks of some ME work or Z3 (inline treadmill, stairs with a pack, etc.).