I pronounce
Vivian and
Vivien the same way. Once I found out that traditionally
Vivian was male and
Vivien was female, I settled on the
Vivien spelling for a girl. The
Vivien Leigh association is a plus.
Vivienne, on the other hand, I tend to use the French "viv-ee-ENN" pronunciation for. I use the English pronunciaiton for
Adrienne, so I don't know why my brain doesn't do the same for
Vivienne. And I wouldn't think twice if I heard
Vivienne being pronounced the same as
Vivian /
Vivien. It's just an odd quirk in my mind.
As for which one I would use as a mn for Elaina (prefer
Elena), I suppose
Vivien. Elaina looks very English to me so
Vivien fits the bill. I reserve
Vivian for boys only.