I'd have to choose
Melissa.
Larissa just gets
Lara's Theme from Dr Zhivago playing in my head. I don't enjoy either of them, actually; if I had to use a -ssa name, it would be
Vanessa.
Melissa Helen, maybe? Keep the Greek theme going. Nothing floral, because of the meaning. And, on the subject of meaning, I prefer the much less frilly
Deborah.