The irony of Lola's solace
Lola is deeply disturbed, and she has an internal thought life that is so different than her experience of reality that she can only feel catharsis when she allows her external circumstances to match her internal turmoil. Thus, she places herself in compromising situations, allowing rapists to have their way with her on the bus. She is ironically destructive, and her behavior is certainly not what one might want for their friend or family member.
Joining the Communists
This detail might seem jarring to the reader, but Lola joins the Communist Party just before committing suicide. The detail is ironic because it seems to imply participation in a group movement, but she is obviously not motivated to participate in life. She seems motivated to do something ironic because she is kicking against the goads of logic in some ways. Her behavior is deeply symbolic, but also confusing and bizarre.
The suicide
Without a doubt, suicide is sadly ironic, because it is the exact opposite of typical human instinct, which is to survive and thrive. Somewhere along the way, she forgot why she should even attempt survival, so she picks something else instead. The suicide has surprising consequences in the lives of her friends and community, and as they mourn her, they also are forced to deal with the consequences of her decisions in other ways too. For instance, the Communists persecute them.
The ironic fathers of the girls
The remaining survivors share an ironic detail that is kept secret until the middle of the novel. Their parents were all Nazis, placing them in the crossfire of both Communists and the government. They are under ironic scrutiny considering their age. They aren't leaders of some movement, they're just school girls whose parents were Nazis, but they are certainly held back by these issues. They eventually graduate, but not without a great deal of paranoia and invasion by authorities.
The dark denouement
The denouement is the passage of a novel that follows the climax like a coda. In this case, the denouement is ironically dark. One might expect that life would let this friend group catch their breath, so to speak, but actually, they are continually haunted by death. Georg dies, and they are concerned that potentially, he was murdered and framed for suicide. Later, Kurt dies, indicating that they are still not safe.
