Memphis Haylie - To be honest, I prefer Memphis on a boy, but I do think this is a cute combo. I actually have a female friend who has the occasional nickname of "Mem," though it doesn't pertain to her actual name.
Leya Ryleigh - It's not my style, but I think it's pretty.
Kairi Hayden - Again, I prefer Hayden on a boy, but this combo is okay.
Leilani - This sounds to me like the name of a Hawaiian princess, though I guess that's not necessarily good or bad. Leilani Grace would be cute, since it's a common short name to balance long, exotic Leilani. Other suggestions: Leilani Mae(ve), Leilani Kira, Leilani Cora, Leilani Willow.
Athena - I personally think this is too much for a child/person because Athena was such an important goddess in Greek mythology. But anyway, suggestions: Athena Vivienne, Athena Beatrice, Athena Gabrielle, Athena Kate.
Rhea (pron. "Ray-uh") - My first instinct is to pronounce it "Ree-uh," but this is a pretty name. This is also from Greek mythology, but not a main deity, so I think it's usable. Suggestions: Rhea Penelope, Rhea Corinne, Rhea Gabrielle, Rhea Isabelle.
Good luck with your name list!