Is it sufficient for my mother to recite one surah after Al-Fatiha in each rak'ah of the Tarawih prayer, or should she repeat what she has memorized from the Qur'an in each rak'ah?

It is desirable for a woman to prolong her standing (qiyam) in the Tarawih prayer, as this was the practice (hady) of the Prophet, peace and blessings be upon him, and his companions. If she only memorizes a certain amount of the Quran, she can repeat it in each rak'ah. The worshipper is rewarded for the standing prayer (qiyam) according to the number of verses he or she recites.