Is the sister who promised her father a monthly sum then went back on her promise considered disobedient, and is the father who cut ties with his daughter because of that considered a severer of kinship ties, and does he have the right to compel her to pay the sum?

If the father is poor, his well-off children (males and females) are obligated to spend on him reasonably. However, if he is not in need and requests money for his children's university education, the children are not obligated to give it to him, because university education expenses are not obligatory. If the daughter donates what she can, it is better, as it constitutes filial piety towards her father, maintains ties with her siblings, and fulfills her promise. The father's command to boycott the daughter is impermissible, and it is not permissible to obey him in that regard. Filial piety towards the father and showing kindness to him are obligatory.