Sharing two before/after images to show the beautiful transformational power of skillful editing. This post is not a tutorial, but I will highlight the important steps I take to achieve this look.
First, I isolate my subject using the quick select tool - then make a new layer of only the subject. Then I fix up my subject - get her skin tone right and brighten eyes, lift shadows, etc etc. These adjustments are not global - they are only applied to the subject.
Next I work on the background. I duplicate my background layer and desaturate those neon greens, adding reds and yellows. Duplicate it again and burn shadows, tweak the colors, then add a matte haze layer. Duplicate it again and add a radial blur - then a gaussian blur. Then add a radial gradient to highlight the light behind her head.
Then I do some masking work to make the stark difference between my subject and the background smoother and not such an obvious piece of photoshop work ;)
And, as you can see in the top image, her cute little empty hands looked like they needed something to hold - so I added an apple :)
The key to editing portraits is to separate subject from background - they each need their own special treatment. Hope that helps!