What does Melissa mean in Latin?

Melissa, a proper noun, means “a bee-nymph in Greek mythology; a daughter of the Cretan king Melissus”.

What is the genitive of Melissa?

The genitive singular is Melissae. Melissa is feminine, first declension.

In classical Latin, [mɛˈlɪs.sa]; in ecclesiastical (church) Latin, [meˈlis.sa].

proper noun · femininefirst declension

Melissa f sg (genitive Melissae, masculine Melissus)

Classical[mɛˈlɪs.sa]Ecclesiastical[meˈlis.sa]

Mĕlissa, ae, f., = Μέλισσα.

I. A nymph who is said to have invented the art of keeping bees, Col. 9, 2, 3.—

II. Daughter of the Cretan king Melissus, who, together with her sister Amalthea, fed Jupiter with goats' milk, Lact. 1, 22, 19 sq

Borrowed from Ancient Greek Μέλῐσσᾰ (Mélĭssă), from μέλῐσσᾰ (mélĭssă, “bee”).