In Harper Lee's To Kill a Mockingbird, by Harper Lee, Scout is something of a tomboy, and her only real friend at the start of the novel seems to be her brother Jem. While she may play on the playground at school, she never speaks of girl friends. She does not bring anyone home. If she gets into a fight, as she does with Cecil Jacobs or Walter Cunningham, Jem pulls her off.
Scout and Jem are very close. When Dill suddenly appears one summer, his ability to role play and his knowledge of various books and movies encourage Jem to accept Dill into their "family." For several summers during the book, Dill, Scout and Jem are nearly inseparable.
In order for Scout to play, she must be willing to follow the "laws" of the boys. It's a little easier because for the longest time, she has always played the "secondary roles," for there was no one else to do so. For a while after Dill arrives, the three greatly enjoy each other's company. They even begin pretending to be the Radley family. However, as the summers pass, Jem starts to mature, the boys get closer, and Scout increasingly feels left out. Sometimes she and Jem argue.
For instance, when Jem starts to tell Dill about "Hot Steam" (ghostly vapors hovering on the ground), Scout calls him on it, saying the tale is nonsense. It is not until later that she realizes how much Jem has resented her contradiction of him in front of Dill. So, as they play a game where one climbs into a tire, rolled up in the center and is pushed—for a ride—Jem pushes Scout extraordinarily hard, directly at the Radley house. When the tire hits the side of the house and Scout pops out, Jem realizes what he has done and screams for her to come out of the yard.
Another time, when the boys plan to go out at night and visit the Radley house, Scout tries to dissuade them. Jem tells her that if she doesn't like it, she can stay home.
Whereas the two had a pretty close relationship, when Dill arrives and Jem starts to grow up, the Jem and Scout are not has close as before when they play, but as seen at the end of the book, they are still devoted to each other.