Linda (The Time of the Doctor)

Linda was a family member or friend of Clara Oswald, who attended a Christmas dinner, along with Clara's father and grandmother.

Linda believed the Eleventh Doctor to be Clara's boyfriend, and was somewhat surprised when he arrived naked. When he sent Clara back to Earth from Trenzalore for her own safety, Linda suggested there were other fish in the sea, and that she had a list of possible replacement boyfriends. (TV: The Time of the Doctor)

Behind the scenes
The Doctor Who website claims that Linda is Clara's step-mother.