How to tolerate Christian family nonsense? How to stay grounded in my beliefs?

It depends on how seriously you feel about it. If your Mom and Dad support her then you are not going to make any long term changes to the way she dresses. If its really important to you you could say "my house my rules", but only if you are prepared to demand that your parents come back or put her on a plane.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.