Prologue
It all started late one December night in a hospital in England. Voldemort, who most wizards feared, and Tina Riddle, who most wizards had never heard of, were having a child who was to be the Heir of Slytherin. Voldemort was in an explicit disguise so the Muggles (non-magic people) wouldn't arrest him on the spot. The only reason they were in a hospital was that a Muggle happened to see Tina when she was about to have this child.
Voldemort had been on a genocidal rampage, killing everybody who got in his way. One night, about half a year after his daughter was born, Voldemort had been given inside information that led him to the Potters. He successfully killed Lily and James, so he went to their baby, Harry. He didn't have much luck with Harry. When attempting to kill him, he lost his own powers and was forced into hiding. Tina died only days later, leaving her daughter to fend for herself in a forest near their manor.
Later that night, a four-year-old boy with flaming red hair was walking around the forest and saw this little girl. For a minute, he just looked at her. She had green-silver eyes and hair that was a curious shade of blue. She held the key to vault 137 at Gringotts Bank and wore a pale green dress.
He walked up to her, taking her free hand and leading her to a grown witch and wizard who had his flaming red hair. They turned out to be his parents, Molly and Arthur Weasley. Mrs. Weasley looked at the girl curiously.
"Where are your parents?" she asked politely.
"Gone," the girl replied sadly.
"What is your name?"
"Diana Slytherin Riddle."
Mrs. Weasley glared at Diana, then whispered something to her husband. Percy, the boy, had not yet developed the ability to judge, so he took Diana in as his own. He taught her everything as he learned it, and she caught on rather quickly. Intelligence was a common trait of the Riddle family.
The Weasley family had many children, and Diana was never accepted as one of them. She had to stand at the table, and she wasn't given meals. She wasn't allowed to access her vault at Gringotts until she was accepted at Hogwarts. Various things like that gave Diana the feeling Mr. and Mrs. Weasley hadn't taken a liking to her. She couldn't quite say the Weasley children didn't like her. In fact, Ginny was jealous because Diana got more of her brothers' attention. The attention Ginny got from her mother made up for it, though.