My sister and I have never had a great relationship which comes down to her passive-aggressive behavior. For example she'll make snide comments and just have an overall negative attitude but if I say something back all hell breaks loose, it's like I have to walk on eggshells around her.
That was before I cared about politics, but now it turns out we have complete opposite beliefs. She's a college professor and teaches a course called "urban studies", and based on the course description it's largely focused on topics like white privilege and climate change. She's also an abortion clinic escort. She's a vegan and hardcore environmentalist. She's basically a stereotype of a millenial liberal and describes herself as a marxist.
I haven't seen her in 2 years but we have a family reunion coming up and I just know that certain topics might come up at the dinner table like COVID. I'm also against abortion and that's another topic that might come up as well. If I give my opinion and say that I think lockdowns over a flu virus were ridiculous and I didn't get the vaccine I'm sure an argument would break out because she gets angry when someone espouses non-leftist beliefs. Last time we had a family dinner she got angry because I simply asked her and her long-term boyfriend if they were planning to start a family someday.
Now I'm considering whether I should speak my mind within limits if these topics come up or just stay silent to maintain the peace.
The best thing you can do is to sit there quietly and let her words roll like water off a duck's back. You don't need to say a thing, as she'll end up making your points in the long haul with her tiresome liberalism. After all, a fool may be thought wise...until they open their mouth.