Idea 1: "The Wizard of Oz" (1939)
Let's say Dorothy is around ten when she initially visits Oz. This is set maybe two years later. In Kansas, Aunt Em and Uncle Henry are killed in a tragic accident, leaving Dorothy completely alone with nowhere to go. Meanwhile, in Oz, Glinda finds herself constantly thinking about the little girl from Kansas. She finds a way to communicate with Dorothy, (the author can work that out), and when she discovers that the girl is alone, she finds a way to bring her to live with her in Oz. (The author can work that out as well.) Now Glinda has to adjust to having a child around, a child who is grieving. And Dorothy has to adjust to a new home, while grieving the loss of everyone and everything she's ever known.
Dorothy settles into life at Glinda's castle, but she's lonely, being left mostly to her own devices. Glinda is busy with her magic, coming up with new spells, and Dorothy doesn't want to disturb her. Glinda doesn't mean to be neglectful. She's just not used to having a child around.
When Scare Crow finds out that Dorothy is back in Oz, he invites Glinda and Dorothy to come and visit him in the Emerald City. While there, Dorothy is reunited with Lion and Tim Man, and they help her open up to Glinda and express her needs.