Zoe Rain Bernstein, of Carlsbad, California, suffered serious brain injuries after her dad lost control of the car they were in and crashed into a lamp post.
The little girl was put into an artificial coma by doctors to reduce brain swelling, but when she woke up her personality had transformed.
Her mum, Kelsie, told Patch: "She had to re-learn how to eat, use the bathroom, brush her teeth, put on her shoes, everything.
"When she woke up out of the coma she couldn't talk. It was completely starting from scratch."
As a result of Zoe's brain injuries, she developed attention deficit disorder (ADD) and behaviour issues.
"Her personality is completely different," said Kelsie.