Since I was not there, so I can't say what was the other lady's intention were. And since I'm a nikon user, I cannot 100% same canon behave the same but just to point out that the LCD is not always accurate.
(note again, this is for nikon)
Basically what you see in the LCD is the JPG thumbsize version of the photo. If somehow you set in-camera edit on your camera, it will reflect on the LCD. But if you shoot RAW, what was saved and what you see are different (historgram, white balance, etc etc). Anyway, just to point out another possible scenario on what you see from other people's LCD. Even in my D70, histogram in my LCD preview is okay but when I look at the raw in lightroom, its mostly 1/2 stop under.