Zainab al-Hilli, 7, was shot and so brutally beaten during the attack that doctors placed her in a medically induced coma.
She has since regained consciousness and was able to hold a brief discussion with officers in France.
Zainab is seen as a key witness to the horrific attack that left her parents and grandmother dead.
Saad al-Hilli, 50, was killed in the family car alongside his dentist wife Iqbal, and her mother, on Wednesday in a remote spot close to Lake Annecy.
Sylvain Mollier, 45, a French cyclist who apparently stumbled across the shooting, was also killed.
Zainab’s younger sister Zeena, 4, who survived by cowering behind her mother, has flown back to Britain with carers. French police believe the older girl could provide them with crucial details to help piece together what happened.
A source said: “They have been able to speak to her but this was just an initial meeting. They could not go into any detail and the child was very tired.”
Police must now wait for a green light from medics before they can engage the girl in a more lengthy discussion when she is expected to be asked about her memories of the attack.
The spotlight in the criminal investigation has turned on the family home in Claygate, Surrey, after police identified items of concern and called in a bomb disposal squad. But officers later said that the unidentified items were not hazardous.
It has also emerged the four shooting victims were killed with the same gun, fuelling speculation they were targeted by a highly trained contract killer.