Sorry you have to deal with that :(
I think I’ve been fairly lucky with friends respecting my choices. The best thing to do is to stay calm and ask people to respect your lifestyle because unfortunately, there are plenty of people who won’t change : / Give them the facts if they make ignorant comments about your diet. Or even straight up explain to them that it’s rude to disrespect your beliefs like that. Too many people don’t realize how important veganism is to us and don’t get how hurtful and rude it is to belittle what you believe.