The concrete will help wear them down a bit, but you may find you still need to trim them. The best way to do this is, once she's used to you and will happily lie there getting her tummy scratched, get someone who's in the habbit of trimming sheeps' feet to give them a quick trim. It's being slightly 'porky' that causes the problem, made worse if they're constantly on soft ground. My wee sow's around the same age and hers are fairly long, but she's showing no signs of discomfort or problems when walking (or bounding
)
She'll be fine purely on grass and a bit of fruit if you feel you've got to give her something (puppy dog eyes have nothing on a pair of hungry Kune eyes
) providing she's not in-pig and as much space as you can give her. Kune Kunes were scavengers, travelling over big areas to find food - my Kunes are always out and about nibbling and don't spend much time sleeping or lounging compared to the other pigs I have.
Ambriel is right with their rule - you should be able to feel the ribs quite clearly and just be able to feel the backbone, if you can't they're too fat. But don't panic, all Kunes are prone to this (just like labradors) you've just got to be cruel to be kind initially but long term it's worth it.