Brooke is an abused child, when her mother and father split up, her mother took her siblings, Josh and Paige, with her. Brooke has always felt neglected, her father abuses her.
One day she runs into her mother, remarried with a child that is a 'half sister' to Brooke.
She sees the torn girl that is her daughter, and realizes that she must get custody of this child, but it's going to be hard.
Since Brooke doesn't want to be with her mother, she senses it will be just as bad as staying with her father.
So she runs away, leaving behind a small note, that says; I'm leaving, the only clue to finding me is the spot.