Sandra Mitchell was the mother of Adam Mitchell. When Adam went to travel in the TARDIS, she believed he was still working at Henry van Statten's museum. Later, when Adam had an implant in his head from 200,000 (which, at the click of fingers, would open a small circle on his head and exposing his brain) he tried to record Internet codes on her phone when she was out. When Adam tried to upload the Internet, and the Editor read his memory to find out the Doctor's weaknesses, he abandoned Adam back at his house in 2012. Adam's mum returned, saying time flies "just like that" and clicking her fingers, then watching in horror as her son's head opened up.
Behind the Scenes
Her first name is never given on-screen or in the credits, but is given as Sandra in Doctor Who: The Encyclopedia.