I think it's difficult to copy EXACTLY what your friend is doing because you aren't your friend! What works for one person may not work for another, etc.
However it might be a good idea to get an idea of what your friend eats and how much. Sometimes it helps to get an outside perspective on this stuff! I know that a big reason I was able to lose weight was because I spent a lot of time with my skinny ex-fiancé. He didn't have a healthy diet, but I saw how he only ate when hungry and stopped when he was full. Because of my upbringing, it was a totally foreign concept to me.
Right now I find it strange when people grill me on what I eat and how much, but I usually don't mind it too much when they feel the need to analyze my habits. It's actually helped quite a few people around me!