Sarah and Emily have been best friends since kindergarten. They share everything, from their deepest secrets to their lunch snacks. However, lately, Emily has been spending more time with a new group of friends, and Sarah feels a bit left out. She understands that people grow and change, but she misses their old routine of walking home together and talking for hours. She's trying to be understanding, but it's hard. What is the main challenge Sarah is currently facing in her friendship with Emily?
A) They are arguing about their lunch snacks.