ماذا تفعل الأخت الكبرى إذا تعذر عليها الاغتسال بعد الحيض في المستشفى حيث ترافق طفلها المريض ولا تستطيع الخروج أو تركه وحيدًا؟

It is not permissible for a Muslim woman to delay performing ghusl after her menstruation ends and the time for prayer arrives. If she prays before performing ghusl, her prayer is invalid, and she must make it up if she finds water and is able to use it. A woman must go to perform ghusl unless doing so would harm a sick child. If harm would result and she cannot find someone to take her place, then she must perform tayammum until she finds an opportunity to perform ghusl, because in this situation, she is considered like someone unable to use water or lacking it. As Al-Kharshi mentioned in his commentary, one of the things that permits tayammum is the fear of damage to wealth or life due to seeking water.