My first reaction was, if she PR’d after a vacation, and she is tired now, give her another vacation. But I am a bit disturbed by the thought that she can run one good race on a day but not two. This might make sense if you were asking her to run a 400 followed by a 4 X 400, but from what you said it seems that 200 is her longest race. It is possible that she is sick. If not, I guess what I would do (like you, I coach HS girls) is give her two or three days completely off then focus on a normal taper with high intensity (95%), relatively short distances, low reps; maybe one session like this this week and one or two early next week. At this time of year, being fresh is most important, IMO, and that should be your focus with her. With my own team, we have district finals this Saturday to attempt to qualify for State. 4 X 400 is our best shot, but one of the girls has a glute pull and is doing no training this week. Another is sick and is doing no training. As long as they are healthy to run on Saturday, I don’t think a week without training is going to be the main issue. If you have a decent base, I think freshness is paramount.
FWIW, my two 4 X 400 girls who are training did 3 X 150 @ 95% with full recovery Monday, tempo on Tues, will do 3 X 60 tomorrow, tempo on Thurs., rest on Friday.