The investigators may need to ask: was her seatbelt fastened?
At that age, she would have had a lap belt attachment on with an adult during take off and landing. knowing small children on planes at that point in the flight she would have likely been out of that lap seatbelt.
The article indicates her parents bodies haven't found yet (not identified in main wreckage?).
Assuming that her and her parents were in there seats (row 9), could there been an event that she (only) was sucked out to account for the distance from the main crash site. The plane made no course change nor declared an emergency, so unlikely.
The fact remains though how did she end up so far away from the main crash site