Is there somewhere in scripture that says the father has to give "permission" (especially if she is grown and living on her own)?
I think it is desirable to have her parents' blessing, and I think it would serve you well to do whatever you could to win them over long before you get to that point. I am sure you wouldn't be pushing your beliefs on them, so I don't see why that would really be a problem.
Christ Church ARP, NC
"Blessed be the God and Father of our Lord Jesus Christ, who has blessed us in Christ with every spiritual blessing in the heavenly places, even as he chose us in him before the foundation of the world, that we should be holy and blameless before him. In love he predestined us for adoption as sons through Jesus Christ, according to the purpose of his will, to the praise of his glorious grace, with which he has blessed us in the Beloved." Eph. 1:3-6 ESV