Now, first i pasted it onto the main picture!
1) I distorted it a bit
2) I used "levels" and "shadow/highlight" options to adjust the colour a little
3)I added a few photo filters (deep emerald, deep blue, sepia..) just to level the colours
4) I added a 3px line around the model (stroke option; linear dodge)
Along the way, i also "ugly-fied" the background with different brushes
Finally, I used the liquify tool to enlarge some parts of her body (lips, knees etc.) and then applied sponge and water-colour tool, again, to achieve a less realistic look of her skin!