Mardah was a Bajoran female born in 2351. Her parents were killed during the Cardassian Occupation of Bajor. Following their deaths, Mardah and her siblings, Sarjeno and Koran, were raised by neighbors. In 2364, at the age of thirteen, Mardah moved out to live on her own. (DS9: "The Abandoned")
In the late 2360s, she moved from Bajor to live aboard space station Terok Nor, which later became known as Deep Space 9. There, she worked at Quark's, where she was employed as a dabo girl. Her career choice caused a rift between her and her siblings, who were not exactly thrilled with her job as a dabo girl. She found it amazing how much people judged others based on nothing more than their job. (DS9: "The Abandoned")
While working at Quark's, Mardah still pursued a full education, attending the station's school, where she was noticed for her writing talents. Keiko O'Brien frequently told Mardah that she should try to get some of her stories published. Despite the encouragement for her to pursue writing, she eventually chose to study in the field of entomology. (DS9: "The Abandoned", "Sanctuary")
In mid-2370, Mardah asked Jake Sisko to tutor her with some of her entomology homework – which was in reality, more of a "study date." Jake was forced to lie to his father, due to her profession, in order to ensure that the two could get together. (DS9: "Sanctuary", "Playing God")
A few weeks later, Jake accidentally told his father about Mardah, professing his love for her. He later admitted to his father that he was unsure how he would react to the fact that Mardah was a dabo girl. To prove to his father that she was more than just a "girl", Jake wanted to have her over so that his father could meet her. After receiving the "go ahead", Jake ran off to inform Mardah of the good news. (DS9: "Playing God")
Despite disapproving of his son dating a dabo girl four years Jake's senior, Ben Sisko finally invited Mardah over for dinner in early 2371 – with the intentions of seeing what he was up against. For dinner, they had Creole shrimp with Mandalay sauce, which Mardah enjoyed, as she was partial to spicy food.
During dinner, while Jake was checking on dessert, Mardah confessed to Ben that although at first, Jake seemed like just another teenaged boy, she had realized there was more to him than that, that he was full of surprises, and that she cared about him very much.
Shortly thereafter, Mardah was accepted into the Science Academy on Regulus III, forcing her to move 300 light years from DS9 – and Jake. She broke the news to Jake on a day they had planned to spend hanging up decorations for the Bajoran Gratitude Festival – the same day, Jake intended to give Mardah a Bajoran earring as a gift. The two subsequently broke up. (DS9: "Fascination")
Mardah, played by Jill Sayre, appeared only in the episode "The Abandoned".
The role was originally to have gone to Chase Masterson; however, Masterson was thought to be too old due to the age difference between herself and Cirroc Lofton. Avery Brooks (who directed "The Abandoned") stated that she might be a love interest for his own character, but not for Lofton's. Masterson had played the role with "kittenesque sexuality", so the producers kept her in mind as they thought she could play a fun character. Masterson was later cast for Leeta in "Explorers" without a clear indication whether she would come back, but due to her performance she became a recurring character. (Star Trek: Deep Space Nine Companion (p. 238)) Another actress who auditioned for the role of Mardah was Tracy Middendorf, who was later cast as the second of three actresses to play Tora Ziyal. (Cinefantastique, Vol. 28, No. 4/5, p. 63)
There was some dispute in the pronunciation of this character's name. In the script for "Sanctuary", it was pronounced as "MAR-duh".  However, in the script for "Playing God", it was pronounced as "MAHR-duh".  The script for "The Abandoned" did not include a pronunciation for this character's name.