Twilight Sparkle, whose real name is Tarah Silver, was a very intelligent 15-year-old who lived with her brothers, Scott Aaron,who was 21-year-old and her adoptive brother Spike,who was 12-years-old.
On September 13th, Tarah's 16th birthday, she and her brother went to buy some things for the party that would be very simple, just for the family, while Spike was with their parents, but while they were in the car on the way to the store, they had an accident. An accident that left Scott with a broken arm, but Tarah's case was more serious, her brain was affected, and because of that, she got a little insane, so she had to stay in the hospital, where her sister-in-law and former nanny Candace worked with her aunts Celestia and Luna who owned the place, she shared a room with a white girl with blue eyes and curly red hair named Polly Paes (Pinkie Pie) who had split personality, they became great friends, even when Polly she turned Polianna (Pinkamena) and said that when she left that hospital she would kill everyone who avoided her because of her illness.
A few days later Polly was out of the hospital, and because of loneliness Tarah's case instead of getting better was getting worse, she saw three girls in that room, and as she was alone, she talked to these girls, she started to get another disease, schizophrenia , which because of this, she said they were all ponies who lived in a magical place called Ponyville in Equestria.
Candace called Tarah's parents and explained her case and her parents suffered a lot from it, but they managed to take Tarah home the next day, they and Candace believed that if she stayed together with people she could get better, Celestia knew Polly's parents,and gave them the address of where she lived for Tarah and Polly to have company, since they both didn't have friends, Polly because of her illness and Tarah because she spent a lot of time locked in her room studying.
Tarah would go to Polly's house and vice versa, once when Polly was at Tarah's house, she started calling her Pinkie Pie, and said her name was Twilight Sparkle, Polly even thought these new names were cute so she decided to call Tarah Twilight, they made some jewels, five necklaces and a crown, which Tarah said were the Elements of Harmony, and that with them, they could overcome all evil, despite knowing it wasn't true, Polly preferred to pretend it was real than contradicting,since for believing it Tarah was happy, she said that her neighbor, Mr. Dominich, the god of discord, who would try to lead them to the side of chaos, her parents moved to live with Tarah so they could take care of her, they were afraid of what she might be able to do for thinking that she, Polly, her teacher, and three imaginary friends were heroines who had the objective of protecting "Equestria", and because of that they were afraid that Tarah would end up killing someone saying they are bad people, for example Mr. Dominich who in Tarah's mind was the god of chaos, she might want to kill him thinking that if she does that the world would be at peace, Tarah is no longer aware of what she does, she might end up doing something terrible thinking that you're doing something good, and that's what your family is afraid of.