Nicola, the elegant Latinate feminization of Nicholas, has long been standard issue for English girls but for some reason has never voyaged across the Atlantic, which we consider a pity, especially as Nicole's standing has waned.
In Britain, Nicola first appeared around 1940, started rising in the fifties and by the mid-1970's had reached third place on the popularity list, after which it began to be replaced by Nicole.
In his novel The Well Beloved, Thomas Hardy spelled it Nichola. Nicola was and still is a unisex name in Italy: one historic bearer Nicola Pisano was a renowned and influential thirteenth century sculptor, Nikola Testa an eminent inventor.
Nicolette, which was the name of an enchanting princess in the medieval French romance Aucassin et Nicolette, is a more feminissima version.