It’s so tough. My eleven year boy has ADHD and we’ve definitely encountered a number of (usually intelligent) people who think it’s made up. My mother in law doesn’t believe in it, and she treats my son terribly. It’s been a journey for us to learn how to deal with it ourselves, and she’s not willing to go on this journey herself. Our view is that spend a lot of time and energy protecting our lovely son from adults who treat him poorly because of his ADHD. We also need to protect him from his angry grandmother. If we have to choose between the two, it may help her realise she needs to educate herself better.