My Italian name dictionary (
Santi e Fanti by
Enzo La
Stella T.)has "quasi solo m." at the beginning of its entry for
Matteo (technically Mattèo). If the feminine form Mattea was
never used in Italy, I assume that the dictionary would say "solo m.", as it does by many other names. Since it says "quasi solo", it probably means that though the feminine form Mattea is quite rare as a female given name in Italy, it has been used on rare occasions.