You should talk about the three main character and their relationship to both illusion and reality.
Tom seems to have the firmest grip on reality. He holds down a job and is the economic foundation of the family. And, although he goes to the movies a lot and craves romance and adventure, he knows well the difference between his dreams and their possible fruition in reality. He is smart enough to separate himself from his mother and his sister, and he will eventually escape from them, cruel as that may be on some level.
Laura, on the other hand, lives in a world all her own; it is a world devoid of basic reality and given over to her own illusions. She has a glass collection of tiny, delicate animals which she constantly polishes and tells herself stories about. She also plays old, worn-out phonograph records. Except for short and sweet interactions with her brother and mother, that's pretty much her life.
Amanda, the mother, is caught between being all too aware of life's harshest realities and the unreasonable belief that some gallant gentleman caller will come into her daughter's life and sweep her away, and they will live happily ever after. She also spends much of her time thinking and talking about the long-gone, privileged days of her youth.