When she spoke to you about how you should complain more when people don't do their job... You might have asked her thoughts on how that might be accomplished.
You could have validated her opinion and gained some insight into doing a better job? Nothing lost by just listening, right?
Never pass up a good opportunity to validate. Just thinking...
You are right, of course. I don't know if it is detaching or growing indifference, but I just wasn't responding as I have in the past on that day.