I absolutely adore
Nell /
Nelle. It's my favorite girl name, as of right now. It strikes me as sweet, gentle, and classy. Like you, I went looking for an appropriate full name for it, but came up with Nichelle.
I doubt the meaning of
Parnel would be a problem, since so few people are aware that
Parnel was once a bad word. Remember that
Molly came back after people forgot that a moll was a prostitute. That being said, I'm not a real fan of
Parnel (too masculine maybe?). What about
Pernel? It sounds like a cross between
Parnel and
Pearl. It's much more feminine to my ears.