I really don't like the sound of Sephy. It sounds really twee to me.
Sephora is okay. It reminds me a little bit of a medical term ... epiphora (falling tears) but that's obscure, I know. And it seems brand-namey because of the makeup store and its marketing. But it's not awful. I think I would like it better as
Seffora, which looks more down-to-earth to me.