The Janitor's girlfriend Lady first appears in S07E01. But the actress who plays her (Kit Pongetti) actually appears much earlier in the series (S02E13) in a separate role credited as Dr. Mitchell :
Actress Juliette Goglia, director Kit Pongetti and actress Elizabeth... News Photo - Getty Images
Kit Pongetti — The Movie Database (TMDB)
Austin Film Festival Special Feature: Kit Pongetti – LiveMom.com – Dedicated to building a better village