Returned as My Dead Twin for Blood

Twenty years ago a pair of twin girls were separated. One of them, Vivian Sterling, went on to make her name in European finance, where she is known as the Finance Queen. The other, Autumn Sinclair, was raised by adoptive parents and has been pushed around for most of her life. When Vivian finally tracks her sister down, she arrives just as Autumn is driven to jump from a building, and Autumn is left barely alive. Vivian takes Autumn's name and her place and goes back into the Sinclair household, with each move worked out before she walks through the door. The engagement banquet is the first thing she wrecks, and she deals with the man Autumn was engaged to there. She goes after the mother-in-law next. She pulls the mask off the adoptive parents, and at a drinking party arranged against her she turns the trap around on the hosts. She wins the custody fight, then moves on the Sinclair family company itself, and the people who hurt her sister find their own methods used on them. Somewhere along this road a businessman nobody can place begins keeping close to her. She cannot tell whether he is an enemy or a friend. He holds a careful distance and helps her anyway, and in time he becomes the ally she relies on most.