She is playing the thing masterfully, smearing her father while basking in the adulation and support of people who hate every firm moral stance he has ever taken.
She's an adult. He's treating her as an adult.
In time, she may realize she has been duped by a lying adversary who has no love or regard for her.
Poppycock.
Apparently he parents found out because they found some magazine she was reading while she was still in high school.
Occam's Razor here. Apparently while she wasn't "public" she could live with her father, in his apartment, and work for him.
The minute she was public...out with her.
I would't be at all disturbed if he had told her ahead of time that she was out of his house at 18 if she didn't change, although I would disagree as to the effectiveness.