My Sophie's mn is
Ophelia (full name
Sophia Ophelia Seraphina); I have the same sort of (illusory) proprietary feeling about it as I do about
Scarlett and
Gideon. I think it's quite lovely, of course. =D
Good mn's could be...
Ophelia AntoinetteOphelia ClaudetteOphelia DominiqueOphelia Josephine (really like this)
Ophelia NaomiOphelia PenelopeOphelia RosalieOphelia Violette
... and of course
Ophelia Seraphina, or even
Ophelia Sophia. :-)
I like the nn
Fifi, personally. It works with my
Sophie's name because the -phi- syllable appears so often; and it's repeated in
Ophelia Josephine above, which is probably why I like it so much.
Good sister names, imo, would include
Scarlett (can't help it!),
Octavia (the O thing),
Claudia, or perhaps something similarly Shakespearean, such as
Juliet,
Miranda,
Rosalind,
Helena,
Bianca or
Cordelia.