Honouring one’s parents is one of the most important duties that people are obliged to do for one another, because Allaah says (interpretation of the meaning):
“And We have enjoined on man (to be dutiful and good) to his parents. His mother bore him in weakness and hardship upon weakness and hardship, and his weaning is in two years give thanks to Me and to your parents. Unto Me is the final destination.
15. But if they (both) strive with you to make you join in worship with Me others that of which you have no knowledge, then obey them not; but behave with them in the world kindly”
[Luqmaan 31:14, 15]
Allaah enjoined keeping good company with those mushrik parents who were striving to make him join others with Allaah sShirk) – He told him to behave with them in the world kindly.
Obeying parents is obligatory for the child with regard to that which will benefit them without causing harm to the child. As for that which will not benefit them or which will cause harm to the child, there is no obligation to obey them in that case.
Shaykh al-Islam Ibn Taymiyah (may Allaah have mercy on him) said in al-Ikhtiyaaraat (p. 114): A person is obliged to obey his parents so long as it does not involve sin, even if they are evildoers… This has to do with that which benefits them and does not cause harm to him. End quote.
As for shunning her, you should not do that, for she is your mother and has great rights over you. You can uphold ties with her by phone and visiting her from time to time. Seek reward by being patient with the insults and curses, etc., that you experience in these visits, seeking thereby the pleasure of Allaah.
But in order to reduce the harm and evil that results from visiting her, you can make the visits few and far between, but keep in touch with her by phone if possible, or by asking how she is. Perhaps she will need you and have some problem. If you do that, there is no sin on you, in sha Allah, if you make your visits infrequent. And do not be disobedient towards her, because – although is the one who is entitled to kind treatment from you – she does not want you to visit her and she is not asking you for that.
You are only reducing the number of your visits so as to avoid the harm she inflicts on you.
We ask Allaah to help you to do all that is good, and to guide your mother, and set your affairs straight.
And Allaah knows best.