I like
Myrna too. I also like
Myra. Of your combos, I like:
Myrna Blythe (love the contrasting sadness and happiness)
Myrna FrancesMyrna FranceneMyrna Magdalene or
Magdalen
I'd also suggest
Myrna Pearl. There's something about the similar sounds that sounds Southern, old-lady-little-girl cute to me. WDYT?