Next time you see her wait until you're both in a happy mood or something and just say to her 'Hey, I know this is out of the blue, but we have such different views on politics and religion that I think it gets us into a bit of trouble. I know I'm really stubborn sometimes and I don't want that to get into the way of our friendship, so let's stick to happy topics eh?"
Hopefully she'll be able to accept that. If she's really like it sounds then she'll probably take it to mean that you know she won't ever 'see the light', but I guess just try and make it sound like your fault. Obviously it's the fault of both of you for not having enough self-control to change the subject since you both know that the other won't change their mind. Neither of you have a hope of converting the other, she's not going to suddenly stop and say 'You know what? You're right, I'm wrong about my religion and politics' so I think the best you can do is see it coming and stop it before it happens by changing the subject.
