It says right on the link that they used Magic Bullet Suite.
Did you need specific instructions on how to set up the negative high contrast layer and then use that as a track matte for color correcting just a portion of the shot? If you do not have Magic Bullet try adding the curves effect and then move the black point from the bottom left to the top left and the white from the top right to the bottom right. Now adjust the curve. Use this as a track matte for an adjustment layer.
Another option would be to use Colorama and apply the negative preset and adjust the position of the black and white pointers on the wheel.
Another option would be to use selective Color . . .
There are a million ways to do this. It's sometimes called the Pleasantville effect. Try Googling that.
Setting up a negative high contrast layer to color correct a portion of the shot sounds like what I'm looking for, yes.
Basically, I know how to do a basic Pleasantville effect where one color stays in the shot and the rest of the shot is desaturated. What I don't know how to do is what they did here, where the flowers are isolated, the woman is isolated, and then the background becomes tinted blue.
But yeah, it sounds like what you're saying will get me there. I do have Magic Bullet Looks as well...can you give me a little more info on how to do what you're describing? I'm something of a beginner in all this, so I'm not sure I followed your description completely.
Thanks so much for your help, I appreciate it!