As soon as Dorothy gets to Oz, the first thing that happens is that she kills the Wicked Witch of the East. This is clearly a reference to her mother, who died in childbirth bearing Dorothy. For further proof of that, note that she first lands in Munchkintown…the Munchkins, with their diminutive stature, clearly represent infants. Further, after the witch is killed, her slippers wind up on Dorothy’s feet…this is Dorothy’s “inheritance”, so to speak. Her protests to Glinda and the Munchkins that “I didn’t mean to kill her”, shows her residual guilt at her mother’s death.
Glinda, who appears at this point, is Dorothy’s idealized version of her mother, glimmering and beautiful, but ultimately, unable to help her. At the same time Glinda appears, so appears the Wicked Witch of the West, upset that Dorothy “killed my sister”, and demanding the slippers the Wicked Witch of the East had. The Wicked Witch of the West is, of course, no one other than Aunt Em (or at least Dorothy’s image of Aunt Em), whose sternness Dorothy fears (Aunt Em was the disciplinarian, compared to her more laid back Uncle Henry), and who she feels resents her for, as Dorothy sees it, "killing her sister (Dorothy’s mother).
Glinda being dead, is unable to help her “get home” (i.e., reenter into the loving family structure that Dorothy feels she misses out on due to her absent mother), so Dorothy has to go to the Emerald City and see the Wizard (Uncle Henry, as will be explained later).
So, Dorothy sets off, and along the way meets her personal insecurities (the scarecrow, tin man, and lion, representing Dorothy’s own feelings of stupidity, fear of inability to love, and cowardice.) These images are so well known that I don’t really have to go into much detail, I’m sure, although I will point out that feelings of inadequacy, emotional abandonment and timidness aren’t uncommon among orphans).
So, after meeting her companions (although, of course, her neuroses really are with her always), she manages to get to the Emerald City, where she meets the Wizard, who seems at first to be a terrifying figure, but, as we will learn, is really less impressive in fact (much like Uncle Henry, who as the head of a rural Kansas family, should be the paterfamilias, but in fact, has turned over the leadership role to Aunt Em.). The Wizard will help her get home, but only if she kills the Witch and brings back her broomstick. (Dorothy has externalized all her negative feelings at her situation…her orphanhood, the poverty in which she lives, etc., and placed it all on Aunt Em. Aunt Em has become, for Dorothy, the source of all her misery. How much better it would be, she thinks, how possible it would be for me to have a home, a real home, if Aunt Em were out of the picture and it were just Uncle Henry and me. We could have a happy home together. There’s no doubt here’s a strong Electra Complex going on here as well.)
So, after leaving the Emerald City, Dorothy is captured by the Witch, who wants her slippers, and is willing to kill her to get them (We’re seeing here, again, Dorothy’s fear of her aunt, who, as was mentioned, she believes resents Dorothy and wants her dead). She accidentally kills the witch by splashing her with water (This, on the one hand repesents Dorothy’s prayers for water, which was on the minds of every Kansan in the depression, but on the other, more personally to her, it represents Dorothy’s supplanting of Aunt Em’s role…pouring water to “keep down the dust” was a common household chore, and by doing it, Dorothy has become “the lady of the house”.
Her mission successful, Dorothy returns to Oz, only to find out that the wizard is a fraud, that her companions possessed all the traits they were seeking all along, and to be informed by Ginda that she can get home by herself. This is a kind of breakthrough for Dorothy…she’s done what she’s prayed for…Aunt Em is dead, and it’s just her and Uncle Henry, but she’s still not happy, she still can’t feel “at home”. But what she comes to realize, indeed by this very failure, is that her insecurities are baseless…she is smart, she is loved and capable of loving, she is brave, and that the cause of her misery was never Aunt Em at all…it was her…she chose to be unhappy, she chose to be alienated, and she can now choose to reverse that.
So her voyage of self discovery over, she now awakes, a wiser and more psychologically integrated young woman, to the loving embrace of her family…her uncle, and yes, her aunt, who she now knows doesn’t resent her for her mother’s death, and who, in fact, loves her (and who, now healed, Dorothy is capable of loving back).