Is it permissible to abandon one's sister due to her disobedience and her committing acts such as breaking a hand and hitting the mother, especially since communication increases the harm?

A limit must be set to the sister's aggressions against her mother and brother, for striking without right is clear injustice and is considered a major sin.

The principle is the impermissibility of abandoning a Muslim for more than three [days], especially a close relative, except in two cases:

1. If the abandonment leads to the sister receding from her disobedience and injustice, because abandoning a transgressor is for a legitimate benefit, and is then considered a form of connection and support.

2. If abandonment becomes necessary to repel her harm, while maintaining the resolve to maintain ties with her and endure her harm. It is permissible to forgo means of connection that cause harm, such as visits and speaking, but not other means.

So, abandonment is permissible if it leads to her receding from disobedience, and forbidden if it increases her aggression, unless her harm cannot be repelled except by abandonment, in which case it is permissible to the extent necessary.