It depends. Harmony is most important. I'm a skeptic, but also open minded. If someone goes to church...this is okay. If someone drags me to church...it's not okay. If someone allows me to listen to Rush, without criticizing...it's okay. If someone refuses to let me watch Rush videos or mocks Rush...it's a problem. The ability to respectfully agree to disagree is a good trait. If she is able to do this, not liking Rush can be forgiven. In other words, if she loves you for who you are, keep her.