Doubt you will be able to reason to reason with your 3 year old the way I did with my 8 year old.
Just keep showing her an alternative. I like rebel8's response, make it look like your wife's eccentric beliefs.
...we talked about Halloween and the holidays and why mommy does not celebrate. "She chooses not to celebrate because she believes that by not celebrating she is pleasing God," I said.
We talked about how different people of different faiths practiced their faith differently even though they are pleasing the same God. I asked her if she remembered the invitation she got from her Mormon friend to attend her baptism. She did so I told her that Mormons feel that they please God by not drinking coffee or sodas because of the caffeine nor do they smoke. They feel that by abstaining from these things, they keep their bodies clean and please God. "So you mean no more Dr Pepper's?" she asked. "If you and mom were Mormons I could not drink Dr Pepper?" "That's right," I said, "if mom and I were to try to raise you up as a Mormon, no soft drinks for us and no coffee for mom." She questioned about how different people's religions have different rules when they are all trying to serve the same God to which I responded, "Yeah, it does all seem a little man made, doesn't it."
...we passed by this muslim couple and my child, being 8 and naturally inquisitive began asking, "Why is that lady wearing a mask and only her eyes can be seen?" To which I replied, "Well, remember what we talked about concerning rules and pleasing God? People of the Islam or Muslim religion believe that women should remain covered from head to toe so as to show respect to their husbands or fathers and in so doing, please God." "Mom does not do that," she said. "I know, same God different rules," I replied.
