Jane Siegfrieda is so cool. I would so go with that. I also really like Wilfrieda.
I know what you mean about the number of letters though. Actually, not so much the number of letters, more number of syllables. But yanno
Minerva,
Cordelia and
Frida could work.
Jane not so much, but
Frida definitely could beat up her big sisters. And the boys are only two syllables right?