Orion slave girls were Orion females that were sold at slave markets. They were also known as Orion animal women, or in the Orion language lodubyaln (literally: "life-contractors"). Orion slave girls were a much sought after commodity due to their sexual allure and appetites. (TOS: "The Cage"; ENT: "Bound"; FASA RPG: The Orions module: Book of Deep Knowledge)
Many Orion females sold as slaves were covert operatives seeking increase their personal wealth and satisfy their sexual desires. Some Orion females, however, were actual slaves.
In 2390, Atria D'blae was an Orion slave girl aboard Drozana Station, until she was sold to an Orion Syndicate agent in 2395. The day before she was sold, Atria sold her daughter, Nita D'blae, to an Orion named Rema to take to Ter'jas Mor and train to become an Orion slave girl as well. Nita's transport was attacked by Nausicaan pirates, however, and she never arrived. ("Becoming Klingon")
In 2407, Atria was still posing as an Orion slave girl while actually being an Orion Syndicate agent who acted as the defacto leader of the scout ship OSS Cluros due to her influence over the ship's commanding officer, Ursan. ("Survivors of Yamatai")