Personally I prefer the frillier
Viviana or Viviane for a girl, but
Vivienne's quite nice too.
Vivien's nms--perhaps because it resembles
Vivian so much--but it's OK for someone else's daughter.
And
Vivian's 100% male to me too, not the least of which is because it was originally so. You're right about its resemblance to
Adrian,
Dorian, and even
Darian. And I'll also put it that both
Oscar Wilde and
Frances Hodgson Burnett had sons named
Vivian (or
Vivyan / Vyvyan, in Wilde's case); it was somewhat common for young boys of their era.
Miranda