Shun shun shun.
If I found out a potential mate voted BNP they'd be permanently unavailable to me. We'd just be incompatible, I can't stand their racist ********.
What's the problem?
Unless she re-gurgitates their manifest every 10 seconds or outside mosques on a Friday, I fail to see why this should have an impact on your otherwise (seemingly) perfect relationship.
It makes you a pussy really, she sounds fun
I think it would be unfair to shun her regardless of her views, give her a chance, if you aren't looking for anything serious then it could be unnoticeable if 'knowing' doesn't bother you. But if it is something that bothers you then ask her about it and in this conversation I think you'll find whether you still want to get involved.
(eg you might find its her parents' view passed on or she might be racist etc)
Ask her why she votes BNP, she's probably naively following her family's political views. She's not necessarily racist scum... There's a degree of hypocrisy here, it's the same as saying 'I'm not going out with her, she's a Muslim, They're all terrorist sympathisers.'
You can't accurately assess people's personalities and views just because they vote for a particular party.