Is she at all lame, and is there any accompanying lesion or inflammation? If so, it could be CODD - contagious ovine digital dermatitis - and you need to see a vet.
When you say you can see the 'soft part' underneath, do you mean that, mainly, the wall of the hoof extends beneath the sole? If so, and you have any hard ground, then she could be wearing through the excess horn which is undergrowing the hoof. This is healthy and nothing to worry about.