You don't actually have to do anything. Just be honest with her and the rest of the family about your political beliefs and call out her cultish behavior. She'll either moderate her ideology enough to be tolerable (at least around you) or she'll throw YOU over, showing how much she really cares about blood. Either way problem solved.
Doesn't sound like a sister to me. Sounds like just another enemy.
No. Still my sister, for as long as I live. If I could just throw her over, I would've never posted. The trouble is she's blood.
What, exactly, am I meant to "do about it"?
You don't actually have to do anything. Just be honest with her and the rest of the family about your political beliefs and call out her cultish behavior. She'll either moderate her ideology enough to be tolerable (at least around you) or she'll throw YOU over, showing how much she really cares about blood. Either way problem solved.