Thela Kazanga was an Andorian shen who was on active duty in Starfleet during the 23rd century.
Kazanga was the daughter of Thoraal Kazanga, fleet captain of the Starfleet Third Fleet. She was born on Arpinza, a planet that had been settled by Andorians.
She knew Pavel Chekov from when they had served together on the Enterprise during its second five-year mission under James T. Kirk. She then transferred to the Invincible, commanded by Captain Philip Styles.
Styles was known for being very "by-the-book" -- he would issue demotions where other commanders would have issued commendations. For example, Kazanga was promoted to lieutenant commander twice -- and busted back to lieutenant twice -- by Styles.
By 2275, Lieutenant Kazanga had become assistant chief of security on USS Reliant, commanded by Captain Clark Terrell. She was reunited with Chekov here, where he was the newly-minted executive officer. (Orion Press: "The Blue Rose", "Like You and Me")