I knew a
Shawna when I was little, and even then I really disliked it. I still feel the same, but now it feels dated too. I do know what you mean about finding names that are so ugly they sort of mesmerize you (your
Mildred, my
Olga), but for me
Shawna isn't one of them. Could I entice you toward pretty, neglected
Sonia instead?
I don't like the "aw" in
Shawna, so
Shauna does look marginally better to me. Seana looks best of all, but I bet you it would be pronounced like see-AH-na more often than not.