How should an illiterate person who does not memorize the Qur’an well pray, such as my mother who cannot read and makes mistakes in Surat Al-Fatihah and Surat Al-Ikhlas? Is what she memorizes from Al-Fatihah sufficient for her? And am I sinful for advising her to be content with Al-Fatihah?

It is obligatory to learn to recite Al-Fatihah to complete the prayer. So, whoever is unable to learn it despite exerting effort, or whose mistakes (lahn) in it are clear (jaliyy), their prayer is valid, because "Allah does not burden a soul beyond its capacity."

Al-Nawawi said: "The illiterate (ummi) is one who does not master Al-Fatihah completely, whether they do not memorize it, or they memorize all of it except one letter, or they lighten a stressed letter due to a looseness in their tongue, or other reasons... This illiterate, stammerer (art), or lisping person (althagh), if they were able to learn, then their own prayer is invalid, so it is unanimously impermissible to follow them. But if they were unable, meaning their tongue does not obey them, or the time was limited and they could not learn before that, then their own prayer is valid."

There is no sin in instructing the mother to limit herself to Al-Fatihah; rather, it is preferable for her, because speaking words that are not Quranic without necessity is to be avoided.