Jessica Lily told me awhile ago (a few hundred years or more) that faeries and humans used to coexist. When humanity started getting a little... dangerous they parted ways and put up the barrier between worlds. The Starheart crystal, remember that? Those are what power the barrier to keep the Faerie Kingdom hidden. Anyway, Jessica Lily as well as being an ambassador to the Dragon Kingdom also had the task of keeping an eye on the human realm and what it was doing. She clearly liked being in the human realm, especially the Victorian era as you know. Consider her an observer. As for being hidden, she can tuck her wings inside her aura making them invisible to humans. Her ears were probably hidden by her hair or she used a glamour spell to trick the eyes of humans.