Final answer:
Scout concludes that she and Jem are drifting apart because they are experiencing changes in interests and behaviors as they grow older, which is altering their once-close sibling relationship.
Step-by-step explanation:
The question appears to be related to the characters Scout and Jem from Harper Lee's novel To Kill a Mockingbird. Scout likely concludes that she and Jem are drifting apart because as they grow older, their interests and behaviors begin to diverge. Jem starts to display a more mature disposition and is less inclined to participate in the childhood games and activities that he once shared with Scout. This drift might also be indicative of Jem's entering adolescence and experiencing changes that Scout, being younger, does not yet understand. In this context, Scout means that the close sibling bond they shared is changing and perhaps weakening as they grow into different stages of their lives. This is a common experience between siblings as they progress through childhood and adolescence.