This reminds me of a movie I just watched Mike. The younger daughter of one of the sisters did not eat meat and when questioned about it at the dinner table by her uncle with all family members present (it was a funeral supper) she said she didn't want to eat "fear." She said all animals feel fear and that right before they are killed, that fear goes into their meat, so she did not want to eat that. They made fun of her and she was not impressed.
I think you are going to have to let this one go because remembering back to when I was a young gal, when dad said I could not do something, it made me want to do it even more out of rebellion.
You can have your beliefs and she will have hers, for the rest of time
Good luck.