Is it permissible for a father to provide for his wealthy married daughter who demands luxuries, and is it permissible to disown her, and what should be done regarding this matter?

If a father gives money to his married daughter for her needs, there is no harm in that, and he is not obligated to give the same to his other children. However, if he gives it to her for reasons other than a specific need she has, then it is not permissible, and he must be equitable among his children in their gifts.

Your boycott of your sister is not permissible, for the Prophet (peace be upon him) said: "Do not hate one another, and do not envy one another, and do not turn away from one another. And be, O servants of Allah, brothers. It is not lawful for a Muslim to abandon his brother for more than three [days]." And for his saying: "A severer of ties will not enter Paradise." Your sister's falling into sin does not justify cutting ties with her; rather, it is obligatory to maintain ties with her and offer her advice.