I think it's plain, dated and boring. I know a
Elsa who has three sisters:
Astrid,
Tora and
Ragna. I know another
Elsa too who has a younger brother named
Lukas and two older half-sisters (I grew up with them) named
Nicole and
Amelie.
I have a hard time seeing
Elsie as a "real" name, in that case I prefer
Elsa nn
Elsie.