From Wiki:
Three singles for Girls Dead Monster are planned for release. The first, "Crow Song", will be released on April 23, 2010; the second, "Thousand Enemies", will follow on May 12, 2010 and the third, "Little Braver", will be sold on June 9, 2010.
Looks like "Alchemy" won't be released? Strange, as it was the big song for this episode.

Anyways, I never thought about the possibilities behind their world. It definitely makes sense that it's more than just the afterlife (be it a purgatory, shared coma, or anything else as Kraco mentioned) so Iwasawa could very well have "accepted the will to live" and thus "disappeared", returning to reality and carrying on with her life.

As for Angel, since we learned that her abilities are manufactured much in the same way as Yuri's group, she is a mystery indeed. According to Yuri's group, if you accept yourself in the afterlife, and become a model "student", you disappear (which closely resembles accepting your fate and moving on), then how come Angel is still around. She is the "student council president", so she seems to be the epitome of a model "student". Could it be she just harbours resentment much like Yuri's group, but sees no benefit in "rebelling"? Maybe the reason she opposes Yuri's group so much is because she wants them to accept their fate, and not become like her? I don't know... just spouting off theories.