explain rachel/rachell's new smoking habit ?

Melinda ends up in the bathroom with her former friend, Rachel, who now insists that people call her Rachelle and who hangs out with the foreign language students. Melinda tries to be cool and get her to acknowledge her, but Rachel just speaks in grunts. Melinda feels like grabbing her by the neck and screaming at her to stop treating her like dirt. She feels betrayed, because Rachel never even tried to find out the truth about what happened that summer. She thinks, “What kind of friend is that?” Rachel has also started a trend among the foreign exchange students to “smoke” candy cigarettes, since they can’t smoke real ones in school. She takes one out in the bathroom and pretends to blow smoke in Melinda’s face. Melinda observes that she needs a new friend - that she needs a friend, period. She doesn’t want a true friend. She just wants a disposable one so she doesn’t look so stupid.

Melinda’s despair is even more evident in this scene. Rachel barely acknowledges her presence and symbolically blows her off with the pretend smoke rings. It makes Melinda want a disposable friend, too, just like she has become.