is good for strep - its convenient dosing
and long action are good. (Lingering strep is notorious for inciting the heart (Rheumatic - often silent and diagnosed after many years) or Kidney
). It is wise to take on suspicion, even before confirmation-
It takes time - generally 2 days or so to notice improvement. Till then she needs additional measures - symptomatic and supportive.
if by fourth day, she is still sick - you need investigations and change of treatment / earlier, if you suspect any complication
Wishing her speedy recovery