I think that you have a good handle as to what's going on,
The sister would really like to be a an elder if she had her way,
So this way she gets to play one,
I think that if it wasn't for your wife you know what to do here,
But you want peace at home and this is very understandable,
I think you're going to go through with it for that reason,
Speaking from my own experience I think you have to say something
Like "I'm happy to catch up but I'm not talking to anybody about faith or religion, I'm not sharing what is very personal to me,
If they don't respect my wishes in my own home, I stand up and help them with their coats,
I think they owe me that respect,
:0)