If agreement over politics is as important to you as agreement over religion and you can’t accept her making shallow political decisions that you wouldn’t make, the relationship if probably going to have problems. Her reluctance to tell you who she voted for and so on also doesn’t sound hopeful. But ultimately, this is about something that’s important to you and she’s shown that she’s willing and able to vote in ways that you’ll disagree with. Either you can accept that (as some other Freepers have, who talk about Democrat-voting spouses) and you should probably just stay away from politics with her or you can’t, in which case it’s probably time to move on. But you’ve got to look into your own heart for that answer. Imagine two scenarios in your mind. A future with her voting for people like Obama and Hillary Clinton or a future without her. Which one bothers you more?
I think I’d prefer to just stay away from politics with her except rarely. I’d probably care way too much about it in the first place for my own sanity. Backing off and focusing on other things may help lift my spirits, and four years till the next pres election is a good while to try to subtly influence her.