Mila was a Cardassian woman, the housekeeper of former Obsidian Order head Enabran Tain for over thirty years. Mila was Tain's closest confidante, since even though she "wasn't much of a cook", she knew how to keep secrets. Mila was fond of Tain's son, Elim Garak, whom she practically raised as her own child. Mila always firmly believed that Garak was innocent of Tain's allegations of betrayal.
In 2371, Garak contacted Mila for the first time since his exile, concerning Tain's whereabouts after the deaths of several former Obsidian Order agents. Mila informed him that Tain had departed in a hurry, and pleaded Garak to help him. (DS9: "Improbable Cause")
When Garak and Tain reunited, Tain idly considered executing Mila as she knew "too much for her own good." Garak objected, rationalizing that she was both trustworthy and a capable housekeeper. In truth, he was as fond of her as she was of him. (DS9: "The Die is Cast")
Mila saw Garak again during the Dominion War in 2375 before her death. Garak, Damar, and Kira Nerys were stranded on Cardassia Prime when the Cardassian Liberation Front was wiped out by the Dominion. Mila sheltered them in the basement of Tain's house, from which they organized a new civilian resistance movement. During a power outage, the resistance fighters were discovered as enemy Jem'Hadar soldiers were searching the city for them. Mila answered the door, and tried to send the soldiers away, but they were determined. She was killed and her body was thrown down the basement stairs before they stormed in. Garak promptly swore revenge for Mila's death. (DS9: "The Dogs of War", "What You Leave Behind")
The Star Trek: Deep Space Nine novel A Stitch in Time reveals that Mila was indeed Garak's mother, however, he was raised believing his father was a man named Tolan rather than Tain. Shortly before his own death, Tolan told Garak the truth about his parentage. After Tolan had died, Mila explained to Garak that Tolan was her brother.