Praise be to Allah the Lord of the Worlds.
You can go to an Islamic judge to prevent this marriage and her father doesn`t have the right to force her to marry his brother`s son. The evidence on this is that it was narrated from Ibn Buraidah that: his father said: “A girl came to the Prophet and said: 'My father married me to his brother's son so that he might raise his status thereby.' The Prophet gave her the choice, and she said: 'I approve of what my father did, but I wanted women to know that their fathers have no right to do that." {Ibn Majah}.
However, you aren`t allowed to rebel against your husband and leave house without his permission so long as he gives you all your rights as stipulated in Sharia.
In case you feared he would harm her, let her go alone to the concerned authorities for protection. We recommend that you reason with him and explain to him the possibility of his daughter becoming "Divorced."
Rest assured that affliction is a universal norm whose taste had been tried by the Prophets and the righteous, so everybody is likely to have a taste of it. But, there is a great wisdom behind it, which is only known to Almighty Allah. In addition, supplicating Allah the Almighty doesn`t necessitate an immediate answer.
The evidence on this is that Abu Hurairah narrated that the Messenger of Allah (PBUH) said: “There is not a man who calls upon Allah with a supplication, except that he is answered. Either it shall be granted to him in the world, or reserved for him in the Hereafter, or, his sins shall be expiated for it according to the extent that he supplicated - as long as he does not supplicate for some sin, or for the severing of the ties of kinship, and he does not become hasty. They said: “O Messenger of Allah, and how would he be hasty?” He (PBUH) said: “He says: ‘I called upon my Lord, but He did not answer me" {Tirmithi}. And Allah the Almighty Knows Best.
