Not saying this is right or wrong but female athletes I coach (year or two younger than your 16-y-o athlete and also basically doing S-L) built up to 3x4x40 hill sprints.
Now in short indoor season but not immediately before a race doing sessions like 4x30 starts / 3x60 in and outs / 60+80 smooth from stand so pretty much same as you.
16-y-o boys tend to get more submax stuff (4x150 or sets of 60s if on S-L) as they are usually stiffer and speeding up a lot at this age (bad combo for hamstrings).
Girls aged 16-plus, I’d start slightly increasing speed volume to help get them home in races as targets become more important but I’m not talking about elites here with unlimited access to massage so putting in 95% work for safety reasons.
Not sure about dropping S-L. Adapt it by all means but wouldn’t make any wild swings in training.
2000m of extensive tempo a week would be in proportion to your 680m of speed work. Is she a real power animal? Is she doing extensive med ball circuits and plenty hurdle walkovers too?
Would welcome thoughts on this from anyone.