How do you 'soften the blow' with your emotionally intense child when you're offering a criticism?

A great example: today my daughter asked my son about something he was saying he'd done in art at school. DD: "was it good" DS: 'yeah, it was ok" (or something like that) DD: "Oh, that means it wasn't good"... Ok, she is socially astute enough to know that it wasn't a nice thing to say (its not like he was offering up self criticism, nor was he looking for any feedback...). I called her in to the other room to let her know that what I'd heard didn't sound very nice - and she flipped out. (Note, I wasn't yelling, wasn't speaking harshly, accusing, etc., just letting her know.) This happens pretty much every time she hears something she doesn't like... (I asked DS after how he felt about her comment - he said he didn't care; I said how would you feel if *someone else* had said that, and he said 'oh, pretty terrible')

Any suggestions for ways to share those less-than-complimentary reviews of our kids behavior when they are warranted? Yes, I could overlook some (and do!!), but sometimes a little feedback is needed... I've tried being gentle, assuming she didn't know that her comment might have been taken badly, etc., it almost always yields the same response.

Anyone else have this problem?