Hayleh Harger was transported by air to Loma Linda University Medical Center after the attack on Easter.
Doctors treated her with 100 stitches and staples in her head.
The dog was brought over to Harger's house by a neighbor, who was watching the dog for someone else.
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"When I turned around the dog was on top of her and he was growling," Harger's mother Debra told KTLA.
"I could barely see her underneath him," Debra said.
"Almost her whole head was in his mouth."
"I just remember running toward her and cussing, and I just remember punching to dog in the face."
The dog is currently being held at the Devore Animal Shelter.
Officials say they are still looking for the dog's owner, and may be forced to euthanize the dog.