There have been a lot of posts since I've been on the site about friends, partners, and family asking how to deal with their religiosity. My issue is slightly different.
I have a sister-in-law (sil) who I am just crazy about. I think I love her more than I do my brother. Anyway, we never talk religion so I don't know where she stands on that, but she does have a lot of beliefs that drive me up the wall.
Recently her daughter (my niece) developed some medical symptoms that have been diagnosed as a thyroid problem. Before the test results came in, my sil decided to put the kid (14 yrs old) on a Mediterranean diet and to cut out all sugar and gluten because that would facilitate treatment. Nope.
There is no evidence that gluten is involved at all. (The percent of people who are gluten intolerant is in low single digits.) And the kid doesn't eat vegetables and only some fruit. She's as thin as a rail. This same sil almost didn't have her vaccinated. If she had not done so, I would have talked to my brother about stepping in.
She means well, she just doesn't understand how to interpret legitimate evidence so she's taken in by a lot of nonsense out there. I hate to see her go off on these pseudo-scientific tangents, so I guess I just compartmentalize and ignore that side of her. Is that how others handle this sort of situation?