Margaret Grey doesn't remember most of her life before he durance, though flashes of come back to her in dreams. She was the child of a rather well-to-do family in New York City. Her father was a stockbroker and her mother was a socialite. She went to college because she was expected to in order to find a successful husband - what's euphemistically known as pursuing a MRS degree. She is intelligent, but was never expected to actually use whatever degree she obtained. She was simply expected to have the diploma to attract the right kind of man to support her.
She was kept for almost seven years, entertaining her Keeper's guests when they came to call and essentially working as her Keeper's majordomo, helping her fellow Lost on the household staff whenever and however she can because, in that awful place, the best one could hope for was to not be noticed by their Keeper.
When she returns, only about three years have passed on this side of the thorns. She remembers very little about her life on either side of the hedge - to this day she doesn't remember where that haunted manor house is - and, considering some of the stories she's heard about the durances of other Lost, she is frequently grateful for that. She didn't even remember her name until she chanced upon her fetch at the University. Her fetch was prepared to kill her if necessary to protect itself but, like Maggie herself, it preferred talking to fighting and they reached an accord. It was graduating a few weeks after they met, so Maggie agreed to stay away from New York and her fetch agreed to not return to Glasgow after graduation.
Margaret changed her last name to Steele and made her home among the Lost of Glasgow, maintaining a romantic relationship with Ian Brennan, the Kindred who first discovered her on her return from the hedge. The two of them were sent to London to assist the Courts there in their negotiations to join the Temple.
Maya was conceived not out of love, but necessity. The youngest of four children, her older sister was born with a congenital defect that required a transplant. However, because none of the family was a donor match, her parents tried to have one more child that would allow them to save the life of their oldest. The effort provide futile.
Maya's first few years were good, and while she was well taken care of she wasn't loved. Her parents saw in her failure, a failure to help their oldest and the failure of their own genes.
When Maya was 5, the Fae came to visit her parents and offered a trade, he would heal their oldest for equal trade. Not stopping to think through the implications, her parents agreed. The next day, their sick daughter was healthy and their youngest was replaced with a Fetch. The family never knew what had happened.
Maya's life in Fairy were hard. A sensitive and affectionate girl, these qualities were tamed out of her as she was crafted into a warrior and assassin, someone without pity who would kill without remorse.
Maya doesn't remember how she escaped her master, but now that she's home she sees her Fetch with the life that should have been hers: a happily married school teacher with children of her own, kids that receive the love both were denied. Thoughts of what might have been consume her, and she seeks punishment for all who have wronged her.
First, she will kill her parents who sold her, one at a time.
Then she will kill the sister that was worth more than her.
Next will come the Fetch that stole her happy life.
Finally, she will burn down the Hedge and lay waste to all of Fairy.