It looks like a fairly busy road. The police have given a timescale between 3-7pm. She was last seen at 3pm. What could she have been doing in that area until for four hours?
I wouldn't think it means she was in that exact location for four hours. I think they're probably thinking more of her turnning up there around 3pm and doing whatever she went there for, maybe stopping off at a friend's and coming out a few hour later, or going for a walk and coming back to the car an hour or two later, or anything like that.
Usually the times are a starting place and then might be reduced or expanded based on new information that comes in. Nothing seems to point to police having any new information come in that could help them narrow down what happened in that time frame or afterwards?