Read other letters about this article
Nowhere in your letter do you consider that perhaps Dad, as the parent who has had custody of Anna since she was 10, has wholly neglected her as a parent. Paying for expensive nannies and schooling does not substitute for parenting. It is unfortunate that her mom is not around, but that means her dad should have stepped up to be a father to her, as most men are capable of doing (like most women are capable of being decent mothers).
Though as you say you were fine with this arrangement when you didn't have to see this girl, the reality of the situation is now upon you. It very likely is the case that you are no longer a match for this dysfunctional father-daughter pair and should admit that. The only alternatives are to suffer through a few years of Anna's presence until she can perhaps be shipped off to college or elsewhere, or that her dad and ideally you as well would attempt to rectify some of the neglect of this girl by committing to caring for her, though it may well be too little too late, developmentally.
I find this father reprehensible as a parent if your description of his involvement with his child, and her current state of well-being is accurate, and you apparently assented to this situation while the girl was kept out of your way, which doesn't reflect terribly well on you either.