Demi-Lee Looker needed emergency surgery after the pellet went through her bone but, fortunately, missed vital nerves.
She was shot at point blank range as she played with two friends, aged three and seven, in Sholing, near Southampton, on Sunday, and police are now trying to trace the culprit.
Demi-Lee's mum Fiona, 27, said: "If the pellet had hit her anywhere else she could have been dead.
"Demi-Lee was with two friends and all of a sudden she came out screaming from nowhere and shouted, 'Mummy, mummy I have been shot'.
"She was shaking and I saw the wound, which was absolutely pouring with blood.
"I do not know why anyone would target her. She was just outside with her two friends."
The mum of two added: "It is just outrageous if they have targeted her. I do not know if I want to let my children outside again after this."
A spokesman for Hampshire police said: "This is a very disturbing incident concerning a young child and we want to get to the bottom of what happened as quickly as possible."