Luma Rahl was an alias assumed by Kira Nerys when she travelled back in time from 2374 to 2346, using the Orb of Time, to investigate Gul Dukat's claim that he and her mother, Kira Meru, were lovers during the Occupation of Bajor.
Kira arrived in the Singha refugee camp and met not only her mother and her father Kira Taban but her younger self. However, the three-year-old Nerys remained ignorant as to her identity. As Luma, Kira was taken to Terok Nor as a "comfort woman" for the Cardassians. She became friends with Meru, and learned that Dukat's claims seemed to be true.
"Luma" was taken to the ore processing center after failing to show the proper respect to the Cardassians. There, she made contact with members of the Bajoran Resistance and volunteered to use her friendship with Meru to try to assassinate Dukat. Kira planted a Bajoran earring made of ultritium resin in Dukat's quarters, but changed her mind after seeing Meru's reaction at a message from her husband Taban. Kira warned Dukat and Meru about the bomb, and vanished after the bomb exploded. (DS9 episode: "Wrongs Darker Than Death or Night")
Shortly after Luma's disappearance, Meru reflected that she had attempted to make her friend understand that she did not hate Dukat and that she was doing what she thought necessary to ensure that her children would have a better life. (TLE - Terok Nor novel: Night of the Wolves)