Waiting for Nick - Nora Roberts

Frederica Kimball had been waiting all her life...waiting to grow up...waiting to become a woman...waiting for the day when Nicholas LeBeck would fall as desperately in love with her as she had always been with him.
Now, at last, she was ready!
Nick didn't know what hit him. Sweet, adorable Freddie, whom he'd always loved like a kid sister, was suddenly looking and acting like a woman--and what a woman! And she was making him feel things no brother ought to feel. The waiting was over...but the wanting had just begun.