Apple is Kin. Influential in Notte’s life and one of Horse’s rescues, she helped teach Notte during his time in the city of Az’Kabek. She is also Six’s lover.
Also, incidentally, Apple is based off a wonderful reader: AppleBison.
Also also incidentally, her natural pigmentation tends toward pink. Don’t blame me. The character demanded it. (And please don’t kill me, Kelli!)