Me too. Love, love Blythe. Actually, my favorite mn for it is Matilda. But that won't work for you. :-)
BlytheMeadow -- Love both names, but together they feel more like a phrase than a name: a blithe / happy meadow. Too distracting for me.
Blythe Avonlea -- Awkward flow. Didn't the male lead in "Anne of Green Gables" have the surname Blythe? Again, too distracting.
BlytheRuby -- Rubies should be happy. Just not in a name.
BlytheSusannah -- Ding, ding, ding! We have a winner -- and not just because the other three don't work for me. Susannah has the perfect calm, salt-of-the-earth quality that Blythe has for me. And the flow is terrific. A+.