Zainab Al-Hilli's state of health is understood to have improved in recent days, allowing her to travel back to the UK.
Zainab left France this morning at around 8am. Police from Britain accompanied the little girl.
Her departure follows that of her younger sister, Zeena, who returned to the UK last week after escaping the brutal attack unscathed. The four-year-old survived by cowering under her mother's skirts but she was only discovered eight hours after the killings.
More top news
Chris Gard and Connie Yates want their nine-month-old son Charlie to undergo a therapy trial in the US.
Labour leader Jeremy Corbyn was unable to provide the cost of his party's key manifesto plans on free child care.
Montana Abdhou was with a group of friends when two men on bikes opened fire.