Real emotions vary in intensity and duration. Fictional characters often fail to return to a calm state. Good writing requires heightened emotions that explain motivations and allow for confrontations. Cruel doesn't describe her. There is a fine distinction between dramatic effect and melodrama.
Emotional dialogue contains hyperbole, with more passion than real conversation.
Also, dramatic dialogue tends toward greater eloquence than daily speech. For years I have waited, patiently, quietly in the background. Now, it's my turn. Audience Appropriate Audience appropriate dialogue does not refer to the content of the dialogue, but rather the language and mechanics utilized by a writer. Each writer must determine what is appropriate content.