What event causes Annabelle to tell her parents about Betty's bullying in the novel, Wolf Hollow?

When Andy and Betty string a wire across the path in the woods between the hill farms and Wolf Hollow hoping to injure Annabelle or her brothers, the wire ends up catching Henry in the head, slicing his forehead and causing him to bleed badly. This is too much for Annabelle, who decides to finally tell her parents about the trouble Betty is causing. Betty, however, lies and blames the wire on Toby.