All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
It is an abominable sin that a father sexually abuses his daughter and it is even more abominable if he rapes her. If he does so with any girl, it is strictly forbidden, let alone him doing so with his own daughter.
However, it is not permissible to accuse the father of rape without evidence. Indeed, the Sharee’ah put some special conditions for proving Zina (fornication or adultery) that are not required in case of other crimes. The crime of Zina is not confirmed except if the fornicator admits it, or with the testimony of four trustworthy men, while the testimony of women is not accepted.
Hence, the statement of this girl or the statement of her mother in itself does not Islamically prove anything against the father, especially that the latter denies it.
Therefore, if this daughter has no evidence to prove that her accusations are true, she should not have claimed that she was raped by her father and she should not have taken him to the court. But if what she says is true, then she has the right to ask for protection from him even by taking him to the court so that he would not continue committing this evil or practice more sinful acts with her. In this case, she would claim his dissoluteness and her fear of his evil so that she will be kept apart from him.
Allaah Knows best.