Anyone have any idea what this is before I book a vet app?
The nails seems to be going black, it's covering up the quick almost.
It's on her back feet on each nail and a little bit on her front paw nails.

Nails seem a little crusty underneath where the black is, don't think there is an odour either.
I really hope it's nothing major she's been through enough as it is!

If you google "nails black on cat" or "claws black on cat," you will find information on what this might be. It could be a fungus. However, it doesn't appear that it could be something really serious. I know kitties do not like trips to the vet. You might want to just call their office and explain things and they can tell you whether you need to bring your baby in to see them.