Do As I Say, Not As I Did
Denise is now responsible and has an anti-drug stance and so when she thinks that her little sister is starting to use drugs, she is determined to prevent her from doing so. She does not want her sister to follow in her footsteps. She turns her room upside down looking for her secret drug stash, which is ironic because her parents' actions in doing this to her is what made her leave home in the first place.
Parental Control
Dennie's parents are relieved to have her back, but they are also anxious to prevent her from leaving again, and also anxious to prevent Susie going down the same path. Instead of learning from the mistakes they made, and loosening their grip on Susie, they give her even less privacy than they gave Dennie, which ultimately drives her away.
Escaping Control
Dennie runs off to join a hippie colony because she wants more freedom. This turns out to be very ironic because her boyfriend exerts just as much control over her as her parents did, and she is still not able to truly make her own choices. Even after she goes home, her boyfriend follows her because hs is not prepared to accept that she has the right to choose to do so when it is against his wishes.
Worrying About the Wrong Daugher
When Dennie's parents find her with her boyfriend, making out, they are angry, frightened and emotionally unraveling in short succession. They are fully focused on preventing a reunion between the two, and focused also on making sure that Dennie stays at home and does not follow him back to the colony. The irony in this case is that they are concentrating on the wrong daughter, and that whilst they are preoccupied with Dennie, Susie leaves home.
Susie's Joy at Dennie's Return
At first Susie is extremely excited about Dennie's return. She thinks that she will now have someone in her corner in the house. The opposite turns out to be true, because rather than taking Susie's side, Dennie acts like a third parent, and so Susie finds that she has less privacy and freedom than she did before her missing sister returned.
