Elle, but only because
Kaye looks overdone with an extra syllable that isn't really there. I actually think
Kay is better than
Elle right now just because
Ella and
Ellie are so overused.
Also, nobody asked but...
Bee: very cute, but nickname only unless it's a pet
Dee: too dated
Ji: ok
Ai: cute
Jay: could technically fit anyone but makes me think of a middle aged guy
Em: good, still nickname-only
Enne: good if it's short for something (
Vivienne,
Adrienne, etc)
Vi: love this as a nickname
Zee / Zi: also good for a nickname