How was Bertha horribly good?

From the text:

“She was so good,” continued the bachelor, “that she won several medals for goodness, which she always wore, pinned on to her dress. There was a medal for obedience, another medal for punctuality, and a third for good behaviour. They were large metal medals and they clicked against one another as she walked. No other child in the town where she lived had as many as three medals, so everybody knew that she must be an extra good child.”