Final answer:
In a typical American family, a child's most beloved and important relative in the extended family would likely be the maternal grandmother, influenced by matrilineal descent patterns and potential primary care responsibilities.
Step-by-step explanation:
If Susan is a typical American child, her most beloved and important relative in her extended family would likely be her maternal grandmother. This is often the case in many American families due to the influence of matrilineal descent patterns, where familial relations focus on the mother's side of the family, with property, status, and clan affiliation being conferred through the female line. Moreover, in extended families, grandparents, especially maternal ones, frequently assume primary care responsibilities for the child due to various familial situations such as parental drug abuse, incarceration, or abandonment.