“She's pretty awesome.”
You're a single guy. You met a girl at your friend's party and hit it off with her. Now your friend is asking what you think of her. You like her, so you say this.
She's pretty awesome.
You use "pretty" before an adjective to show how much of that quality something has.
"Pretty ___" is somewhere between "kind of " and "really". It basically means "a little more than you expected". For example:
This soup is actually pretty good.
I think I have a pretty good shot at getting the job.
That song is pretty catchy.
The word "awesome" is a casual way of saying "great" or "wonderful". Actually, the meaning of the word has changed a bit over time. So 20 years ago, you would have used "awesome" to describe something that was really amazing, but today people often use it to describe things that are just good.
It's used mostly by people in their mid-20's to mid-30's but can also be used by younger or older people without seeming strange.
When you describe a person as being "awesome", it means that the person has a good personality and is fun to be around.
People often combine "pretty" and "awesome". It's a funny expression because "awesome" is supposed to mean "great", but "pretty" has sort of the opposite effect. Other similar phrases include:
That's pretty great.
This kind of phrase sounds like something a young person would say in a casual conversation. It would be strange in a formal business setting.