The scene would be there even if you aren't in a relationship with Maddie. Maddie works in the best clothing store in town (more on that and on Maddie in 0.27) and is an aspiring dress designer, so Martha, Emma, Debbie, Lisa, and other girls would continue going there and would befriend her. Her turning point was at the birthday party. She was invited by Daphne and Emma because of the DnD game. She felt out of place for most of the party, especially because she misunderstood Erika about the nature of the topless party, but she felt at home during the DnD game.
Once the DnD game finished, she was one more in the group of young girls. Emma could be pushy once she discovered Maddie was a designer who completed her "fashion gang" (model, photographer, artist, and designer).
In 0.27 you will see more about how the rest of the girls feel about Maddie (especially Lisa, and tangentially Eva, Emma, and Meemaw).