Marjane meets Julie at the school in Vienna, and Julie introduces her to Momo, Thierry, and Oliver. We don't really get to know any of them very much (Marjane doesn't talk about hardly any of her friends for more than a chapter) aside from Julie and Momo.
Momo is the eccentric of the group: someone with a Mohawk, round glasses, unusual earrings, and a unique fashion sense, who goes around saying things like "life is pain" (24.28). We have to wonder how much of this is purely a persona, a façade he puts on for show. He kisses everyone on the lips when he meets them, even men (technically he is Marjane's first kiss) and is fascinated with death. However, he gets a little irritated when Marjane, who has seen plenty of death first-hand in war-torn Iran, turns out to be more of an expert on the Grim Reaper than he is.
We see a little more of Julie, and we do mean more of Julie. When Marjane moves in with her, she realizes that Julie is—gasp—having sex. And outside of marriage, too. (And outside of her bedroom… and probably outside of the apartment… Julie is very liberated.) She's even on the pill. Yes, that pill. She also dates "mature" (22.4) men and smokes and drinks.
All of this eventually rubs off on Marjane. Julie's liberated attitude ends up liberating Marjane as well—she even does her makeup for her. We doubt Marjane would be smoking pot, drinking alcohol, and having sex if she was still in Iran, or living in the boarding house with the nuns.