I feel your pain. My mother has the habit of asking a question and knowingly not paying attention to your answer. Then lieing about hearing you, only to have no idea what you have sad. She does not have the ADD excuse though.
Best thing to say: "They are wrong."
Or: "It's my money"
Or: "I don't believe in keeping snakes together, other people do."
Or: "When you get your own snake, you do what you want to do"
Or: "Whatever."