You run the risk of being ostracized by a conservative social group if you share any opinion that contradicts the teachings of the church school. I'm straight, but the hicks I went to high school with shouted every homophobic slur they knew at me anyway, because my opinions sounded "gay" to them.

That being said, you could tell her that the church has held opinions in the past, which they decided to change when we learned more about the world. The church persecuted Galileo for suggesting that the Earth revolves around the Sun. They called Leonardo da Vinci a necromancer for studying human anatomy. And 98 years ago, Christians wanted to hang John Scopes for teaching evolution in Tennessee.

Basically, if you can't tell her directly, you can at least suggest that the church is not infallible when it comes to certain topics. Again though, people will consider you subversive even if all you're doing is relaying pure, historical facts. There's no safe way to contradict a zealot.