Brenda joins the Scranton office on the "Booze Cruise", ostensibly to evaluate Michael's "leadership training exercise" with an eye towards possible having Michael give it to the other branches. More likely, she was sent by Jan to keep tabs on Michael and make sure the cruise does have a legitimate business purpose. Her presence on the cruise pressures Michael to repeatedly interrupt the festivities to give another lesson in business leadership. An introductory deleted scene suggests at least some awareness of Michael and Jan's history - when Michael requests a moment alone with Jan, Brenda tells him that she was told to say no if that question came up; when he asks again, she instantly agrees before Jan tells her to stay.
In the episode "The Carpet", Jim leaves her an awkward voicemail message, asking her out. In the episode "Take Your Daughter to Work Day", it is speculated that Brenda is Jim's date when he politely declines a dinner invitation from Abby, Kevin's fiancé's daughter. Brenda called Jim in the episode "Drug Testing", but Jim couldn't answer because he was under Pam's jinx.