She is a psychiatric patient, what is due on her family towards her?

Q: My 28-year old daughter has been ill since early age. She does not perform Salah (Prayer) in a correct manner yet sometimes fasts Ramadan. We saw many doctors in the Kingdom (of Saudi Arabia) and abroad, but no treatment has been found for her case of insufficient mental development. Sometimes, she helps her mother in preparing tea and cooking. Some people told me that it is not permissible to eat the food she cooks because she does not offer Salah. We would like to know: What is due on her and what is due on us for her according to Shari`ah (Islamic law) so that we will not be in error? May Allah guide you.

A: We ask Allah (Glorified and Exalted be He) for her recovery. (Part No. 11; Page No. 148) You should treat her with kindness, order her to perform Taharah (ceremonial purification), and carry out the acts of worship as much as she can; for this you will be rewarded. It is permissible for you to eat the food she cooks as long as her hands are Tahir (ritually pure).May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.