Does the anger and outrage of the mother and siblings towards the grandmother who has reached the most decrepit age, lost her mind, and defecates and urinates everywhere, affect their expected reward from Allah, considering that they are committed, recite the Quran, and maintain their prayers?

Expressing complaint and discontent goes against the perfection of patience, and it may diminish the reward but does not invalidate it. The poor woman does not control her own affairs due to her loss of consciousness, and their anger does not change reality. The Prophet, peace and blessings be upon him, forbade anger. The elderly woman should be treated with kindness and dutifulness, and one should not be annoyed by her actions or raise their voice at her.