@Qelix
It would be nice and even better if he could add her to his collection without killing her. But whatever happens, I hope he adds some of those ice elves to his collection.
@xts
I'm not so sure that neither he nor his shadows gained any experience here. They don't always show it when he does. Given what he said earlier about not wasting that ice bear's experience, I doubt he would use his shadows in this manner if no experience were to be had for either of them.
If his shadows alone gain experience, then it's worthwhile for him, due to the fact that their strength is part of his strength. Even if he were A-rank, but had an S-rank shadow, he's still effectively S-rank himself, as long as he can survive long enough to summon his S-rank shadow.