Humans shed millions of microscopic skin cells (called rafts) on a continual basis. As a person moves along, these particles leave an invisible trail that is detectable to a dog. Some fall to the ground or catch on blades of grass, trees, or other obstacles, while some are carried along on air currents. The closer the dog is to the 'victim' the more concentrated this trail becomes.
In light of this, I would say, yes, she got in a car if the trail ended at the corner.
Let's follow your thought a little further ... If the car was a cab, the cab driver would have come forward with info, wouldn't he? As far as I know, no cab driver info exists. If the car was not a cab, it would have been driven by SOMEONE SHE KNEW, wouldn't it? I mean: she didn't hitch-hike, did she? If it was driven by someone she knew, why didn't that person come forward with information - unless he/she drove Chandra away with bad intent? Who could that be?