Summer Wroniecki broke a bone in her leg when the inflatable was blown about 150 yards into the crowd at Duffus Park in Cupar, Fife, on Saturday afternoon.
Summer had previously battled a rare type of cancer, which was diagnosed just after her third birthday.
Her father Christian wrote on Facebook that his daughter was "comfortable".
He said: "Summer is a tough cookie as you all know and will again bounce back."
Mr Wroniecki posted on Monday morning that her operation would be taking place on Tuesday.
It is believed an adult was also treated for a shoulder complaint after the incident.
Organisers said every safety precaution was risk assessed.
A six-year-old girl, who survived a cancer battle, is back in hospital after being injured when an inflatable slide blew into a crowd in high winds.