Everything known about the donne di fuori comes from sixteenth and seventeenth century Inquisition trial transcripts, an adversarial record built from interrogation rather than celebration, and no source independent of that prosecution says how established the belief already was when the trials began.
What would resolve this A Sicilian civil, notarial or ecclesiastical record predating the sixteenth century that references night-gathering spirit-women under any name would show the belief already existed before the surviving trial record begins.
Openhistory and folklore studiesGustav Henningsen, in Bengt Ankarloo and Gustav Henningsen (eds.), The Ladies from Outside (Henningsen)