If
Jane Doe has a daughter, and gives her both the surname Doe and the fn
Jane, then the daughter could be called
Jane Doe II.
But if
Jane Doe has a daughter, and gives her her own name, but the father's surname, then
Jane Smith (the daughter) couldn't be called
Jane Smith II, because there isn't a
Jane Smith I (married names don't count).
Junior doesn't apply to women in any case other than possibly a nn. The next-door neighbour on the cartoon
King of the Hill calls his daughter
Connie Con
Junior, obviously because he wanted a son.
Hope that's a little more clear!
Miranda