How does one character betray another in the story Day of the Butterfly by Alice Munro?

Helen and Myra become friends, although, their real connection is questionable. At the end of the story, Helen accepts a gift from Myra, who likely will not live to see her next birthday. Helen accepts the gift, and then tells us (the reader) that she's going to let her brother break it. Accepting something you don't want, and allowing the other person to believe you are thankful, all while planning its destruction..... is a form of betrayal.