Final answer:
Kanda is upset because the great-aunt of the baby, also named Aissatou and an important namesake, was left out of the christening as the ceremony took place before she arrived.
Step-by-step explanation:
Kanda, the grandmother in the story "Grandmother's Letters," is angry about her cousin's christening celebration because someone important had been left out of the ceremony—the great-aunt of the baby, also named Aissatou.
This great-aunt, being a namesake of the baby, should have been a featured guest at the celebration.
However, the ceremony proceeded without her due to her late arrival, leading to her missing both the celebration and the gifts that were being distributed afterward.
Her anger was compounded by the fact that she had been waiting for someone to fetch her for the event.