During Season 8 Susan has a brief relationship with Dr. John Carter after they both admit that they had a crush on each other when he was a medical student and she was a resident – it doesn't last, as Susan realizes in the episode "Secrets and Lies", that Carter is really in love with Abby Lockhart. She then tells Carter to "tell her" about his feelings. The two both break up on good terms and remain good friends throughout the rest of her career at County. Her problems with Chloe resurface when her niece Susie goes missing in New York after leaving a distressing voicemail message on her aunt's phone. Susan flies to New York (in a crossover with "Third Watch") and discovers Chloe doped up, sleeping rough. Towards the end of the season, Susan faces one of her most difficult story lines, as her best friend Mark Greene reveals to her that his brain tumor has returned. The two rekindled their close friendship as she helps him come to terms with his diagnosis. Susan is alluded to in Mark's goodbye letter in "The Letter" when Mark comments that he had to leave the way he did, even though there were things of a more personal nature to say. After her best friend's death, Susan warmed up to other friendships in the ER with Abby Lockhart and Elizabeth Corday, and was able to work better with her old colleague Kerry Weaver. Dr. Romano, who actually respected her (he once told another doctor to get Dr. Lewis when he had a medical emergency, calling her "the least annoying person down there"), also promoted her to Deputy Chief of Emergency Medicine much to Kerry Weaver's dismay.