I know what you mean about "-etta" endings. But
Fiammetta has a charming quality to it that I find very appealing.
Fiammetta sparkles (no pun intended.) I think it's the "Fia-" beginning that is so unusual. It intrigues.
Constanza,
Eleonora and
Fiammetta sound fantastic as sisters. Don't mess with that trio. :-) I especially love seeing
Constanza being considered. What a kick-a$$ name.