I think writing the letter is a great idea and much better than a phone call. This letter could be kept on file. I don think many people are happily skipping to pick up food stamps - it's humbling. She had no right to make you feel less entitled or paint you or all bipolar patients with a broad paintbrush. She doesn't know anything, until she's walked a mile in your shoes. You can also request you don't want her to help you next time.

I live right across the Michigan border and it's close to 60, which is unusual for this time of year.