Winnie Clarence was a student, later a research graduate, at Snowcap University in Antarctica by 2048. Her name was short for "Oswin Clarence". When she was eighteen, Winnie came to Antarctica because she wanted to explore.
In 2048, Winnie rescued the Twelfth Doctor and the original Clara after they narrowly escaped a helicopter crash near Snowcap, with the two not recognising each other's appearance underneath her heavy snow gear. When Clara entered inside Winnie's room to clean up and get changed, the two got out of their uncomfortable snow gear and they realised that they were doppelgangers of one another, with Clara immediately realising she had encountered an echo for the first time. Later, after overhearing the Doctor and Clara discuss that Winnie was born to die so that the Doctor might live because of Clara splintering herself throughout time and space, Winnie, upset by what they were saying, ran off on a snowmobile. Clara tried following after Winnie but the two fell down a crevasse into an ice cavern. While Winnie tended to her injured leg, Clara told her about how the echoes were created, and Winnie revealed that she felt like she remembered some of the story already.
In the cavern, Clara and Winnie discovered the missing students had been experimented on, engineered by Dr Patricia Audley to survive in extreme cold. Along with the spy Paul South, Winnie released most of the imprisoned humans from captivity after Clara allowed herself to be captured while posing as Winnie, causing Dr Audley to drop her guard as she didn't know about the two of them.
Winnie pretended to side with Dr Audley and betray the Doctor and Clara by letting the Doctor die, and instead tricked Dr Audley into showing the Doctor the signal that caused the animals to go wild. The Doctor transmitted this signal with his sonic screwdriver, and in the confusion, Winnie threw the Doctor the key so he could rescue the remaining prisoners from their cells, stopping Dr Audley's plans. Winnie saved the Doctor's life by pulling Dr Audley into a vat of liquid ice after Audley pulled a gun on him. Dr Audley was killed, and Winnie appeared to be killed as well. Clara immediately made the decision to leave the Doctor and live out her life as Winnie, but Winnie survived when she unwittingly had a syringe of Dr Audley's experimental blue blood serum injected into her, allowing her to live inside the ice. Winnie's roommate Marianne pulled her out of the ice, where she reunited with her mother, Mabel. Clara realised that this meant that not all of the splinters died saving the Doctor, and several of them had lives of their own. (COMIC: Blood and Ice)