Is it permissible to boycott a sister who is about 50 years old, lives with me and her husband in Kuwait, creates many problems, and does not wish me well, and what is the consequence of that?

Maintaining kinship ties is a religious obligation. And whoever wishes to have his provision expanded and his life prolonged, let him maintain his kinship ties. Relatives should not be treated with severance even if they sever ties. Rather, the one who maintains ties is he who connects with those who cut him off. For the Messenger of Allah, peace and blessings be upon him, said: "The one who maintains ties is not the one who reciprocates, but the one who maintains ties is he who connects when his kinship ties are severed." And whoever maintains his kinship ties despite their severance, will always have a supporter from Allah Almighty.