Thalia was a female humanoid child in the 23rd century, and was the daughter of Eurydice in the alternate reality.
She was held for ransom by the Dark Market Syndicate until her mother could pay back her debts; upon her mother's delivery of members of the USS Enterprise, she was released.
After Eurydice regretted her decision to betray the Enterprise crew, Thalia helped operate her mother's ship, the Spectral, to enable them to escape. (TOS - Eurydice comics: "Part 1", "Part 2", "Part 3")