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It sounds like she never got out of the Electra Complex stage. There is also the question about "why her father allows her to act this way"
You believe that she manipulates him, and he has to be willing to be manipulated. Even after you've spoken to him, neither she nor he changed this old pattern.
She could be projecting ill feelings towards you that she holds towards her own mother. You're with her father now and the identified target. She may be acting this way to intimidate you purposefully to leave her father. That way she can continue to behave the same way (because he allows it) He's in a way contributing to her behavior by enabling her to act this way.
As far as what you can do that you have not already done- really not much except keep your boundaries clearly defined, confront her father with specific examples of their behavior, or accept that if this person has a true personality disorder( these disorders are not curable per se, but can be managed if the one having the disorder is willing to change)