I think they don't really need to fall out more so as grow apart. I think it works better considering how friendly they were when they finally met back up. The introduction of Emma was to have a bit of innocence put into Alex's life. I haven't gone into great detail about it yet but I'm going to start in these flashbacks about his life before he escaped.
The beating Alex gave Rick was over the top and he carried on like an animal. The whole school judges him except for his sister (Riley) and Emma so he looks to Emma as a source of comfort as well as a symbol of innocence because his sister has started to ignore him to fit in.
The way I saw what was going on was that Riley was ignoring Alex in school and mostly at home because she wants to fit in and be cool, also explains why she lost her virginity to Jeremy. Now she is suffering with the consequences, having her picture posted around the school. A more interesting root would be to have Tiffany be the one who sent the picture around? At first Riley is mad but for fear of losing everything she submits and stays friends with Tiffany and her crew of bitches. Probably because Tiffany gives some excuse as to why she did it.
What do you think of that?
Also, Alex is going to go after Jeremy when he finds out.
p.s. I know Tiffany is Jeremy's brother so it seems twisted and perverted that she would take pictures of his having sex with Riley but hey it adds to the dark underlying theme of the roleplay.