|Family|| Unnamed mother (current status unknown)|
Jeremy Wolff (fiancée, deceased)
|Occupation|| Former DCRI agent|
Former JTF-12 member
|Portrayed By||Siena Goines|
|First Appearance||Today I Do|
Tsia used to work for the French federal agency DCRI and was later assigned to Interpol. She became part of JTF-12, a team formed after 9/11 by Interpol that specialized in profiling terrorists, utilizing infiltration. The team consisted of Emily Prentiss, Sean McCallister, Clyde Easter, Jeremy Wolff, and herself. At some point after the team disbanded (for unspecified reasons), she and Jeremy went into a relationship and eventually got engaged.
When Ian Doyle, a terrorist she and the rest of the team captured, escaped from prison, killing a motorist and stealing his car in the process, Prentiss becomes concerned for her former teammates and contacts Tsia, who tells her that Doyle thinks that Lauren Reynolds, the alias Prentiss had to go by when she infiltrated Doyle's organization, is dead from a car accident.
Later, Tsia realizes that Jeremy perished from an unspecified natural cause and calls Prentiss, who is confident that Doyle ordered Jeremy's hit and tells Tsia to go into hiding. Having no other options, Tsia does so.
After Sean McCallister and his family are killed by Doyle, Prentiss calls Tsia and Clyde to help her track down Doyle and kill him. The three of them communicate by disposable cell phones at a plaza, Tsia told them she was devastated that she could not attend to Jeremy's funeral. They told Prentiss that that they started their quest of Doyle, having Tsia used her contact in Washington D.C. to track him through one of his alias and found out about his travel schedule. Using one of his aliases, Tsia and Clyde managed to find Doyle and told Prentiss about this.
Prentiss started to distrust Clyde because he didn't tell her that Doyle was imprisoned in North Korea and not in Russia. Finally believing that Clyde could no longer be trusted and that he was hiding information to them, Prentiss instructed Tsia to meet her at an apartment room whose significance is never specified. But when Tsia arrived, she was shot in the forehead through the door and killed by Doyle, thus leading to the belief that Clyde was the mole. When the BAU discovered Tsia's body, Prentiss was devastated that she led her dear friend to her murder and even threw up outside.
It was revealed in Lauren that it was in fact Jeremy who was Doyle's informant. Knowing this, Clyde withheld information from Tsia, who was Jeremy's fiancée and therefore could have been involved in the matter.