Stellar's mother was shopping with her daughter on Iceworld.
On a visit to the ice cream parlour, Stellar's mother complained to Ace about lumps in her milkshake, which resulted in Ace pouring the drink over her head. Ace was subsequently fired by Anderson, who assured Stellar's mother that the milkshake didn't stain.
Stellar's mother got separated from Stellar when the little girl wandered off, resulting in Stellar and her mother being two of the few survivors in Iceworld. She eventually found Stellar by the the Doctor's TARDIS and gave her a ticking-off for wandering away. (TV: Dragonfire)