Eh. The fact that they're girls doesn't change a thing for me, but it might make it worse. Not only are they nicknames, but they're boyish. Your poor daughter may very well get tired of hearing "That's a boy's name."
For
Billie, what about
Willa,
Wilma,
Wilda,
Willemina,
Willow,
Bilhah or
Bilyana?