Is she actually growling at the pups, or is she warning you to stay away? She may still be confused as to what these little things are and could be telling them off

;-) I've never had this where a bitch will growl at the pups, but I have had one tell me to clear off, at least until she was more settled.
I wouldn't leave her alone with them, but I also wouldn't try to interfere unless necessary. I would watch from a short distance just to keep an eye on them if I were you.