I’m not sure you fully understand OCD.
Would you ask someone with a different health condition or disability to do something they can’t just to make others more comfortable? Or would you accept that this is part of who they are and, because they’re family and you love them, tolerate it for a short time?
When I visit my mother-in-law, her home smells strongly of cigarettes and dog. She doesn’t smoke with us there, but the lingering smell affects my breathing, and there’s fur everywhere—including on the furniture. It makes me uncomfortable, and my compulsions kick in—I want to wash my hands, check my seat, and so on. But it’s her home. I don’t demand that she stop smoking indoors or keep the dog off the couch before I visit. Instead, I remind myself that I care about her, and I can manage an hour before leaving.
When I visit friends, they love keeping the windows open—even in the dead of winter—for fresh air. They also don’t mind spiders. More than once, I’ve been sitting there, anxious, as a spider scurries across the floor or lingers on the wall. They don’t rush to remove it because, to them, it’s normal. So, I adapt—I sit with my bag on my lap and my feet off the floor, knowing I’ll be home soon.
The point is, people live in ways that others might find uncomfortable all the time. But for some reason, it’s always those of us who keep our homes exceptionally clean who are painted as “difficult” or “unwelcoming.”
If OP’s mother-in-law is genuinely unkind, that’s a different issue. But if simply visiting someone, sitting at their table, and having tea and cake feels like an unbearable hardship, maybe it’s time to reflect on why that is. After all, respect and tolerance should go both ways.