My guess is: The car had a coolant leak, the offending parts were replaced and she was test driving it. Either the second electric fan kicked on and she noticed because she was paying attention or the temp light came on because the system wasn't full. Nobody is that prepared for a car problem, she gets out with a kneepad already on, doesn't even have to think about who to call. Going back the way she came also makes me think test drive. I was doubting AC condensate because of how fast it makes a spot, but lack of steam or growing of the size of the wet spot makes me think the condensate was just loading up and stopping caused a lot to fall off at the same time.