Answer:
Cumulative Rewards
Step-by-step explanation:
Cumulative rewards are those that have been acquired or collected through time.
In this case, Sylvia's friendship with Sarah goes back a long time, and has rewarded Sylvia in many ways during that time. For this reason, Sylvia has developed a emotional bond with Sarah that goes beyond a transactional relationship, and prompts her to continue being friends with Sarah despite the current shortcomings of the friendship.