Why does Holling's sister leave? Do you think this is a smart choice?

Holling's sister Heather leaves for California primarily in order to find herself. Bearing in mind that the story is set in the 1960s, Heather is just one of countless young people—many of them self-proclaimed "flower children"—wanting to escape the restrictions of family life to find freedom in the big wide world. Heather sees herself as a free spirit and cannot fully express herself in her normal, everyday life. The only way she can do this is to escape, and as far away as possible. California is the perfect destination for her new voyage of self-discovery. It's the epicenter of the hippie movement, of the rapidly developing counterculture in American society.
Although it's a bit of a leap in the dark for Heather, it's probably the right decision on the whole. After all, there's not much happening on the home front; her father sees to that. He's not exactly demonstrative when it comes to showing love towards her. And he goes out of his way to make sure that Heather's home life is about as staid and as stifling as it's possible to get. His word is law; what he says goes, and if that means that Heather's not allowed to go to college, then that's just the way it's going to be. It seems that Heather really has no choice but to take off. She may well come to regret her decision, but she'll probably regret it even more if she doesn't at least try to take her life in a positive direction. It's now or never.