Is the original image the actual original photo? It seems to be very low resolution and quite blocky in its colour reproduction.
Nevertheless, I pulled a couple of OK keys in PhotoKey 2 Pro:
With light spill:
Without light spill:
If you could upload the full quality original I could probably get better results.
To get these results, in the Key settings I lowered the detail to 0% and raised the level to 11%. I also changed the spill suppression to 'Extended' to remove more of the green spill on her lower leg.
A couple of masks were applied, one to remove the top-right bit and one to clean up some fluff underneath her back.
As Axeman says, photos where the subject is so close to the greenscreen can sometimes prove tricky. The dark shadowing under her back is the most problematic element - in future try to get some more light down there.
Hope this helps!