The Outer Limits (1995) : 6x11

Anne Reynolds is a cold young woman, estranged from her mother, Laura, haunted by memories of her dead father and terrified of intimacy of any kind. Then one night, while repairing a flat tire she is attacked by a mugger. Severely wounded, she dies on the operating table only to come back to life five minutes later. However, it soon becomes clear that something inside her has changed. Anne learns she was one set of Siamese twins and her mother agreed to an operation that killed her sister, Marie, while allowing Anne to live. Now the remnants of Marie are starting to assert themselves changing Anne.