I’m not a professional in this stuff or anything, so take this with a grain of salt, but it sounds to me like the two of you need to sit down and have some heart to heart talks about your feelings. Like what you feel about these things, what she feels about them, etc. And I don’t mean “feelings” as in “I think the dems are awful” or “I hate Stalin”; those are more like beliefs/worldview. I mean drilling down to the raw emotion of it, as isolated as possible from judgments/descriptions of the other. For example “I feel scared when I think about communism” or “I feel alone when you say I’m a ‘Stalin worshiping tankie’.”

Communism has a lot of fear-mongering baked into it in the US, so it’s easy to have people who on the one hand feel abandoned by everyone else in their life for believing in it and on the other hand, have people who are terrified of the implications of anyone in their life who does believe in it. Once you know how each other feels, then you can get into dealing with it. For example, if she’s scared of you being communist, you could explain what communism means to you and talk in more detail about what you do in the day to day of volunteering. Or if you feel isolated by her acting this way, she could try to make sure it’s clear that she appreciates you in spite of any fears she might have about your political beliefs.

What the feelings would look like for each of you is something only you know. The examples are just to help illustrate what I mean.