When first introduced to Winnie, the reader realizes that she is not a happy young girl. She is an only child and has parents that are constantly watching over her. Winnie longs for a little bit of independence. She deeply desires some alone time, or simply something to divert her parents' attention away from her for a bit. The following quote will help:
"See?" said Winnie to the toad. "That's just what I mean. It's like that every minute. If I had a sister or a brother, there'd be someone else for them to watch. But, as it is, there's only me. I'm tired of being looked at all the time. I want to be by myself for a change […] I'm not exactly sure what I'd do, you know, but something interesting—something that's all mine. Something that would make some kind of difference in the world."
After Winnie meets Tuck and the Tuck family, Winnie's feelings start to change. She is still the center of attention, but it's different with the Tucks than it is with her own parents. With her family she feels trapped and scrutinized. With the Tucks, Winnie feels more like the life of the party. It's not all fun and games for Winnie with the Tucks though either. She takes on a sort of leadership role. The Tucks are eager to tell her things, be near her, and show her stuff, but they also look to Winnie for comfort and support (kind of like Wendy in Peter Pan). Winnie is getting the same amount of attention from both families, but one family makes her feel grown up and the other family makes her feel stifled.