I would intervene, not so much because you think he might hurt her, which he may not, but because SHE needs to learn that you're the boss, not your other dog. You don't want them working out their own ranking system and leaving you totally out of it. It's also not his place. I would be more hesitant to correct him for warning her off of his things/food/etc., but it sounds like in a short amount of time, he's decided he's her guardian, and as odd as it sounds, I've seen this turn problematic quickly when he decides YOU can't be around his new charge. Far-fetched, probably, with what you've said about his temperament in previous conversations, but I have a friend that this happened to recently.
I, too, have had the "mother's little helper" dog as I called it. It's ok, most of the time, but it can get hairy when you really start working w/the pup and you're correcting her and then he jumps in to reiterate what you just told her Even if none of what I warned about above ever happens...it's not good for the pup's development.