Can the find my iphone app be wrong?

I looked at my daughter's location and it said that she was at work but then showed her 1 mile away from work for part of the day, then 3 miles away and then back to the location 1 mile away then back to work. She is telling me she never left work but I don't believe her. Could she be telling the truth?

If it always shows her at work from previous days (meaning that map area is correct), then I would guess she went to lunch or something like that.