Is it obligatory for a mother suffering from Alzheimer's, who cannot perform the prayer correctly nor remember its rulings, to pray, or is prayer waived for her?

If a mother suffering from dementia reaches the stage of continuous dementia, then neither prayer nor any other act of worship is obligatory upon her, as the obligation (taklif) is removed from her, and there is no need to remind her of prayer. However, if her mind is sometimes absent and sometimes returns, then she must perform prayer when she is lucid. Her recitation of only Surat Al-Fatihah does not affect the validity of her prayer, as other surahs are sunnah (recommended). The first Tashahhud is obligatory, and the last is fard (an absolute obligation), and she should be taught it. If this is difficult due to her old age, she should pray according to her ability.