Hoof wall non-growth wouldn't cause laminitis but laminitis can cause hoof wall problems, like seedy toe.
It sounds like your instructors horse just has crappy feet, like Tuffy. Always gonna be one problem after another. If she doesn't already have the horse on a biotin supplement, she should try it.
It may be. He is trying to get his horse to a vet, but he has to rely on somebody else who has a trailer that the horse can step into without stepping high. I haven't asked him the mare's history of her feet or anything because I can't make a diagnosis and I don't want him to think I am trying to do that, or implying that he isn't feeding his horse well or anything like that.