Is it obligatory for an 18-year-old sister who suffers from learning difficulties that prevent her from reading, writing, and arithmetic to perform the five obligatory prayers, especially the Salah, knowing that Salah is obligatory for every sane, mature, adult?

A girl who understands speech and comprehends answers is obligated to pray and perform the five daily prayers. She must be taught ritual purity (tahara) and how to pray. This obligation does not cease merely because she experiences learning difficulties, for the obligation is lifted only from the insane and the mentally deficient.