Mothers can be horrible monsters, like everyone else. It's not really your call wether this was "needlessly" hostile or simply an outburst against feeling addressed by a simplification that can be very hurtful when you're on the wrong end of it.
Someone said above they like when HN gets emotional; well no, when only positive emotions are allowed that's just being soppy.
So here's to people with a splinter in their paw, may you find peace.
edit: I don't have narcissistic parents, I don't think, I was drawn to this sub because of other people in my life; but it's a very supportive place, one of the parts of reddit that are purely awesome: http://www.reddit.com/r/raisedbynarcissists/ (notice how Mother's Day is quite the issue for a lot of people)