Best thing to do if those people are often in your life is to talk to them and try to explain. Sometimes being blunt is better than being unable to stand up for what you’ve been through. If they still continue to put you through it? Then you aren’t rude for protecting your mental health.

I have had to work on boundaries. Setting them and sticking to them. You have to be blunt. You are not being rude, you are protecting yourself. "I do not want to talk about this topic. If you continue to do so, I must leave." And if they continue, follow through. Nobody is responsible for your triggers, except you. If someone says something that upsets you, you must walk away. It sucks and you feel like the worst person on earth, but you are the only person who can remove yourself from things that cause you distress. My triggers are common topics and I have to walk away from many conversations to avoid a meltdown, fortunately, it gets easier the more you do it. You dont owe anyone an explaination or an apology. You have a responsibility to care for yourself first and foremost.