She probably came with Mike one day since she wanted to see her friends again but this time Mike isn’t employed as security. That or she is older and ran off without him.
QUESTION. MIKE IS CONFIRMED TO BE REPLACED BY JEREMY FITZGERALD IN THE FNAF MOVIE 2. HOWEVER, MATHEW LILLARD (WILLIAM AFTON) AND PIPER RUBIO (ABBY) ARE CONFIRMED TO RETURN IN THE SEQUEL. HOW IS ABBY RETURNING IF MIKE ISN'T?