I took the words "he's very capable of jumping" to mean that the horse is trained to jump. If he is, and he's just choosing to go through the jumps, he's probably just being lazy, which is why I advised using a crop. I've never met a green horse that would go through jumps. In my experience, they all leap over obstacles like they've got teeth.
I agree that the type of jumps she's using can be taken into consideration. If she is using PVC pipe, it probably doesn't hurt the horse when he runs through it, however, if she replaces the PVC with solid wooden poles (that's assuming she can get her hands on them), that may only fix the problem under certain circumstances. If she switches back to PVC poles or goes to a competition where they use PVC poles, then her horse could go right back to crashing through them. The crop, in my mind, IF used properly, will tell the horse "I don't care under what circumstances we are jumping, you must always go over, not through the jump."