I was acting on 'pure' intuition/instinct. [=only because of intuition/instinct and not for any other reason]
Don't expect me to believe you're '(as) pure as the driven snow'. [=morally perfect]
The relationship is over, 'pure and simple'. [=the relationship is completely over]
(..) By fairest blood it was done. And only by fairest blood can it be undone. You were the only one who could break the spell and destroy me. And the only one, pure enough, to save me. You don't even realise how lucky you are never to know what it is to grow old. No... (..)2012 Snow White and the Huntsman