Six Letters or Less
Isaura ee-SOW-rah - Way too hard to pronounce
Lilaia lil-EYE-ah - eh
Lilia - LOVE! especially with nn Lili
Aemilia - too hard to pronounce and sounds too much like Amelia
Artemis - I don't really like godess names for real people
Astraea - How to say it?
Illyria - Same as above
Isabeau - OK
Liliana - nice, but only with nn Lili
Nerissa - too much like Marissa
Sabrina - Like it
Virelai - Pretty, but same pronunciation problem
Zenobia - Nice
Eight Letters or More
Cordelia - Very pretty. Love the nn Lia
Cressida - too Hunger Games-ish
For middles, even though it is a bit mainstream, I LOVE Rose.
You have a stunning list. I'm quite fond of Isabeau, and the only ones I dislike are Naomi and Amelia, as I just don't like the sound of them. Nerissa, Artemis, Sabrina and Zenobia are just great. They have quite a bit of history to them. I see you took Belphoebe, Calypso and Camellia off you list, but I love those too.
I love your list! I see our styles are quite similar :)