“Man! She is going to flip out when she hears about this.”
Your younger brother wrecked your parents' car. Your mother hasn't heard about it yet. He tells you about it, and you are imagining how angry your mother will be when she hears the news. You say this about what you think her reaction will be.
Man! She is going to flip out when she hears about this.
The expression "Man!" shows strong emotions, like shock, fear, admiration, envy, surprise, annoyance, etc..
Man, I am so exhausted.
Man! This computer is taking forever to start up!
Man! What a gorgeous sunset!
You can use "Man!" when speaking to both men and women, because you're not saying it to anyone. You just say it to show an emotion.
"Man" is casual, but it's completely polite. It's a lot more polite than other words with similar meaning, like "Shit!"
To "flip out" means to temporarily become crazy with anger, fear, or excitement. It's usually used with negative emotions:
Why do you always flip out whenever I say anything even the slightest bit critical?
But you can also use "flip out" in positive situations meaning someone is becoming really excited:
Vince flipped out when I showed him the video quality of the new camera.
In normal conversational English, you would shorten this to "She's going to" or even "She's gonna". But one way to emphasize a phrase in English is to say each word of the phrase clearly and exactly, without shortening any of it. So this phrase is pronounced with a slow and regular speed, and stress on each word of the phrase:
She - is - going - to - flip - OUT when she hears about this.
This expresses more emotion than just saying the sentence with normal conversational speed and stress:
She's gonna flip out when she hears about this.