Answer:
(Fatwa: 252/56=TL/1430)
Not being physically fit is not a valid reason that allows your sister to demand talaq. Your sister should serve her husband as much as she can. The hadith gives glad tiding of Jannah to such wife (whose husband is happy with her and dies in the same state). On the other hand, a woman demanding talaq without exigent condition has been sternly warned:
أیما امرأۃ سألت زوجھا طلاقا في غیر مابأس فحرام علیھا رائحۃ الجنۃ (مشکاۃ 2:283)
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband
