I believe the correct answer is: "Mom, it is normal for a person to experience minor depression in the initial stages of bereavement."
Based upon the information provided by the text, you should tell your mother that there is no need for psychologist as it is normal for a person to experience minor depression in the initial stages of bereavement. Since grandmother lost her adorned dog, she is in state of mourning as she deprived of a friend through their death.