The connotative meaning of a word, is not the denotative, or dictionary, meaning of a word. Instead, the connotative meaning is the emotion that is conjured by a word. (How it makes you feel). Therefor in the sentence when Angela shouts that her brothers are immature, she is meaning that they are stupid or wrong for the actions that they have taken. You can pick up the meaning based on her tone, which is angry. She has been embarrassed by them and feels shame.