An FBI agent, Lily rose up in the ranks and got herself a job where she was in touch with U.S. and foreign ambassadors who would contact her first whenever Americans abroad were in great peril. Through this job and her association with Jack Garrett, she was able to share some history with Hotch and Rossi. Sometime prior to Beyond Borders, her brother went to Thailand, the trip being his first overseas. He had stubbornly believed his American passport symbolized invincibility. As a result of his vulnerability, he was framed for a crime he did not commit and was arrested by Thai authorities. Lily became dedicated to solving the case and finding the real perpetrator ever since. She was recently able to get some leads in the case, but they went cold.
Lily is first seen having a conversation with new agents about international jurisdiction when she is called over to investigate a case involving the abduction of the Sullivan family in Barbados. She had previously investigated the unsub when he killed another family in Aruba in 2013. While on the way to the plane, Lily, Jack, and Matthew Simmons meet up with Morgan and JJ, and they all discuss the case on the plane. Lily is paired up with Hotch and they explore the local marketplace. There, they discuss about Lily's brother and Hotch offers to assist the investigation, but she kindly turns him down. Just then, they spot a taxicab and investigate it, but no one is on it. All of a sudden, they spot the driver, and Hotch pursues him. When Hotch tackles him, he finds cash, cocaine, and passports in his bag, but realizes that he is not the unsub and has the police officers arrest him. Later, Lily looks up on the computer and finds information on Jerry Tidwell, a suspect. Afterwards, she and Hotch use a helicopter to find the boat Tidwell is using to hold the Sullivans captive. After Tidwell is killed and she is informed that the son Nick was thrown overboard, she uses the helicopter's searchlight to locate the boy. After the case is solved, Lily celebrates with Hotch, Rossi, and Jack. Then, she and the others watch as the Sullivans are reunited with their relatives.
- Lily was planned to appear in Criminal Minds: Beyond Borders as a main character. However, the character was dropped from the main roster after Anna Gunn left the project for unspecified reasons. She was replaced with Clara Seger, played by Alana De La Garza.