I agree with
@GatorFL on that. However, no one is making the assumption that she must have been in the building to have been a 9/11 victim. There are other possibilities, but they're remote. For instance, there were some victims in an adjacent hotel—but not many, and I haven't heard specifically whether any of them remain unidentified or whether any of the known occupants of the hotel are among the missing.
Law enforcement had cleared the area around the buildings, so aside from first responders, there shouldn't have any people around the perimeter of the Twin Towers unless they were evacuating the towers or nearby buildings. Theoretically, a few people could have snuck into the area in defiance of law enforcement, but not many would have done so, if any.
There are 1.106 known or suspected victims whose remains have not been identified. Many of those are victims whose remains were burned too badly to extract DNA (at least with 2001 technology), and quite a few of those are thought to have been on the planes themselves or on the floors that were hit by the planes, where there were intense fires caused by the jet fuel. Some remains may have been completely cremated. Fires continued to burn for quite a while, so any victim in any location could have been incinerated, but it stands to reason that any victims from outside of the buildings stood a better chance of being found and identified.
So it would take a confluence of several improbably events for Sneha to have been killed outside of the buildings and to have remained unidentified. She would have had to be near the buildings even though nothing places her at the scene, she would have had to have been in an area where no one was allowed to be, and she would have had to have remained unidentified despite being in an area where remains had a better chance of being recovered and identified than those on the upper floors of the floors of the buildings.
There are reasons why the 9/11 commission initially resisted adding her to the list of victims.