Is it permissible to boycott one's sister or hit her to force her to wear the legal hijab, knowing that she wears a head covering and wide pants, and her parents approve of that?

A brother should assist his sister in obeying Allah the Almighty by advising and guiding her towards hijab with wisdom and good counsel, not with harshness or severity. This is especially true since gentleness is emphasized for a caller to Islam when dealing with family members. Boycotting people who commit sins is permissible if it is highly probable that it will be beneficial; otherwise, reconciliation is more beneficial. Boycotting is a remedy to be used when needed and when its benefit is anticipated. If boycotting worsens the situation, it is not permissible. It is not permissible for a brother to beat his sister to force her to wear the hijab, as he has no authority over her in this regard. His role is limited to advising, seeking assistance from their parents, and reminding them of their responsibility towards those under their care.