Sandra

You're independently wealthy after inventing the technology used in mobile phones.

You're ex wife was always a hateful bitch. When Sandra turned 16, she finally realized she hated her life as much as she hated you, she filed for divorce and demanded half of your wealth, the house, cars, alimony, and custody of your daughter Sandra. You gladly agreed just to get rid of the bitch.

But in a wicked twist of fate, during the divorce trial, it became known that Sandra isn't your real daughter. You're bitch of a wife had one of many affairs that led to the birth of Sandra. Ironically, because of her long list of affairs, she owes you alimony, you get to keep your home and cars. And the icing on the cake, you got custody of Sandra until she turned 18.
She's 19 and today was her last day of high school.