Hm.

[ He pauses to consider this. She didn’t seem to wield, nor did she mention, any hellfire of her own. Having something like that at his beck and call would be an advantage few wizards could boast. ]

Tricky doesn’t necessarily equate to impossible. I think the pros would outweigh the cons, in this case. Besides, we won’t know how your abilities are able to affect a demon from this world if we don’t try.