Gabi's character in the film is free spirited, and in many ways just young. There is no concept of maturity although, she feels she is mature and pretends to engage in adult acts. She really is just a child, and is looking for support and guidance from her older brother. Gabi's has had a hard time dealing with the separation of her and Sam's parents, and accepting her father's new partner. Gabi is hoping to get support from her brother however she ends up seeing him act out the same way as their father.
The story looks at Gabi's relationship with Sam as she explores art herself in her unique way. Sam's art work which pieces together society, and social decay is beginning to take off. The uniqueness of Sam's art with regards to behavior mimics the decay of Gabi and Sam and the ability to make clear wise choices. The characters desire for something fresh, fun and new is there, however the lack of commitment or dedication are not present. Gabi is a great girl, and as I mentioned she acts exceptionally free, and this freedom is a way for her to learn about herself, although some of how she learns is not conventional. She really is looking for someone to understand her and be there for as a male role model, and Sam needs to step up to the plate to replace that father figure.
Gabi and Sam both do and say things that will leave you thinking societal decay with respect to young people. However being not so old myself (depending on your perspective) the decay is from within due to deeper issues that need to be resolved. I personally would never be as free as the characters in this film, and I am sure there are many others out there that are similar to me in thinking, and behavior, however that is why we enjoy the arts, and do not necessarily create them. We can see fresh new ideas and concepts through a different light which often come from much experimentation, and experiences in life, that some of us will never experience due to our own boundaries, and limitations.