Marguerite, hands down.
Isabella is so overwhelmingly popular its obscene and
Eleanor I just find boring, there are so many more fun El-names to be had and it just has a dry cracker feel to it.
Marguerite is fun, vivacious and classy. Being a more traditionalist nicknamer myseld I'd go with
Maggie or possibly
Margot.
Marguerite would need a strong name with a kick to it I think.
Marguerite Elaine,
Marguerite Tamara,
Marguerite Meredith (if one was fine with the alliteration),
Marguerite Persephone,
Marguerite Angelica etc.