We need a better set of photos.
Would it be likely that she typically left the home from the basement? I guess that depends on what rooms they have there. The kitchen is usually the main "get ready for the day" room for most people. My bet is that the kitchen, living room, family room and the like are on the 2nd level of the three.
I just checked that "street view" pic again and discovered how it can be manipulated. Wow! That's amazing, I've never played with G-street view before.
I was wrong, there is no glass on the lower part of the door so a stairwell could not be seen if it cut across behind it. But the window to the right of the stoop, in the basement, would also be in conflict with a stairwell in that spot. I'm pretty sure the only way into the garage is the big door.
As someone said; it's no biggee with a remote door opener. With a remote car starter you could open the door and start the car from inside the house. Not a particularly good practice but one that is probably practiced by a lot of people. The car could have been all warmed up and ready to go when she came out and hopped in.