I always want to follow Blithe with
Spirit.
Blythe, though, is lovely.
Dinah Blythe doesn't sound good at all to me because of the double /eye/ sound. Bleh. If you're going for DEE-na, then
Dina,
Dena, or
Deena would be more appropriate. I think you could find another way to create the oh-so-Southern combo you seem to be going for. :)
Dinah Blanche would work better.