I like the "you're crazier than I am" line, as a line, but of course I don't recommend saying it out loud. Which you know already, since you wisely refrained. I would have also been tempted to call that woman everything but a human being. "Either show me your medical degree, or shut your mouth," is another thing I've wanted to say but didn't.

When people think depression/anxiety/bipolar/PTSD is ONLY a matter of being self-centered, and deny that it's an honest-to-goodness medical condition.... ugh.