I like
Milena (mih-LEH-nah), am pretty neutral on
Melina, and really dislike
Malina.
I think
Mirabelle is nice enough, but really can't see an adult
Mirabelle. It's sort of cutesy and frilly, especially spelled that way (as opposed to Mirabel). I
LOVE Mira, though, and it would age gorgeously IMO. You could still have
Mirabelle be your own special nickname for her (and I think that's really cute).