I think that anyone who would borrow another person's cookware to use as a toilet for an animal is an arrogant, thoughtless, moron. You were not out of line, she was -- big time!
And as for the "what's the big deal comments" above, I suspect that about 90% of the population would never use the pot again, even though it can easily be sterilized. The picture of a chicken-poop encrusted pot is hard to get out of one's brain.
That said, I suggest that you boil some water and vinegar in it and then give it a good scrubbing with some Barkeeper's Friend.