Is it permissible for a woman to sever ties with her parents due to their severe mistreatment of her, and her father's threat to confine her to their home and prevent her from returning to her husband?

First: Tribulation is a divine سنت in which Allah tests His servants with ease and hardship.

Second: Being good to one's parents is obligatory, even if they are disobedient (fasiqin) or disbelievers (kafirin). However, obedience to them is not obligatory in acts of disobedience to Allah. This is indicated by Allah Almighty’s saying: (وَإِنْ جَاهَدَاكَ عَلى أَنْ تُشْرِكَ بِي مَا لَيْسَ لَكَ بِهِ عِلْمٌ فَلَا تُطِعْهُمَا وَصَاحِبْهُمَا فِي الدُّنْيَا مَعْرُوفًا) "But if they endeavor to make you associate with Me that of which you have no knowledge, do not obey them, but accompany them in [this] world with kindness." And the Prophet (peace and blessings be upon him) said to Asma: "Maintain ties with your mother."

Third: If visiting your parents causes continuous harm and distress, interferes in your life, or causes separation between you and your spouse, then there is no blame upon you for refraining from visiting them altogether, and suffice with phone calls and the like. It is also permissible to move to another country far away from them. If their harm ceases, you may resume visiting them. And frequently supplicate for their guidance and well-being.