If 7mo is back to drinking her formula and her diarrhea is decreasing/getting better, do i need to keep re-infusing her with pedialyte?

Not necessarily: Pedialyte is a safe fluid for oral hydration when a kid can tolerate the oral route.It is essentially has the same effect as IV fluid at the hospital. Once a kid is tolerating formula well enough to wet diapers every 6 hours, they can stop the Pedialyte. Pedialyte has no medicinal effect, it just helps and can help avoid a trip to the ER.

No, You don't need.: If your child is tolerating formula with decreasing frequency of diarrhea, he is recovering from the insult and you could gradually feed formula in normal manner.