Is it permissible for my mother to recite Surat Al-Ikhlas after another surah following Al-Fatihah in every rak'ah, out of fear of recitation errors or because of her love for it?

We hope that Allah loves your mother, for it has been established that reciting Surat Al-Ikhlas is a reason for Allah's love, and it is permissible to conclude the prayer with it. It is preferable to follow the Sunnah of the Prophet, peace and blessings be upon him, in recitation, but there is no harm in reciting "Qul Huwa Allahu Ahad" with another surah or by itself after Al-Fatiha. We also advise your mother to recite what she masters from the surahs, even if they are short, to avoid errors, and unintentional errors in recitation after Al-Fatiha do not affect the validity of the prayer.