Great shot.
As for PP, usually you don't want to sharpen too much, or else it will show a lot of the skin's faults, unless you want to soften it yourself, though your girlfriend seems to have flawless skin.
The tone really depends on how you want the photo to feel (just like any other photo), as long as the WB doesn't seem out of wack. I don't usually add vibrance, as it makes the skin more orange/yellow.
A bit of C&C on this photo:
1. Never cut body parts at their "hinges", i.e. wrists, elbows, knees, etc. Usually you should cut at the middle of the limb, so your eye "imagines" the rest. Here, you cut her at both her wrists.
2. Shoot with a bit less head-space here. If you framed just a bit lower to see more of her hands/legs, and a little less above her head, IMO it would fill the frame much better, and fixing problem from #1.
3. Maybe shoot a step or two to your right. That way you'll be able to see more of the clocktower's silhouette, as opposed to being blocked by her hair.
That's pretty much all I can give you. Lighting is great, WB & contrast looks good!