Actually, I do think bio-security is a bit ridiculous if you let your birds outside or,wild birds can get into your barn or coops. Wild birds are a much more likely vector of disease than visiting people.
Can't make out the comb. If she's Old English she should have a single comb. Color looks closest to a Blue Golden Duckwing-sorta. Not a Crele & definately not a Creole [whatever that is].
She'd be a $50 hen if someone was willing to pay $50 for her. If all you could get for her was a dollar she'd be a $1 hen. On the other hand, if you got $200 for her she'd be a $200 hen. Chickens don't have an absolute value. They're worth whatever someone is willing to pay for them.