She (rightfully) hates the sandwich technique, where you build your criticism into a protective fog, to keep your colleague from feeling like you have criticized him. Which you have. But now he's not sure.
Or, I suppose, it would mean that you mix your praise for his good behavior with criticism... to keep him from getting the swelled head? Whatever.
I think I'd like to know if I'm effective. Even when I was feeling very self-conscious and unhappy, I would take criticism because I want to be better. I prefer "don't do that" to "you know, you're all really good person and make good hot sauces but...."
I guess it takes all types. In IT/Software, I would suppose many of us follow some older, wiser advice.