Well, she used Petrificus Totalis of course! What else would you use to Petrify a person?

I suppose the kingdom was happy because it was peaceful and people had what they needed and at least some of what they wanted and they got along with each other most of the time.

The witch hated cheerfulness because that's just the sort of witch she was. I guess if she had other reasons I'll find out later when I write more.