Answer:
(Fatwa: 171/27/TL=1431)
Khula can take place only with the consent of both parties. Therefore, if husband is not ready for khula, it cannot take place without his sign. But, if the husband of your sister is addicted to drinking and oppresses your sister, then your sister can raise the issue to the local Shariah Panchayat or Darul Qaza.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband
