Ah, happy chance! the aged creature came, Shuffling along with ivory-headed wand, To where he stood, hid from the torch's flame, Behind a broad hall-pillar, far beyond The sound of merriment and chorus bland: He startled her; but soon she knew his face, And grasp'd his fingers in her palsied hand, Saying "Mercy, Porphyro! hie thee from this place They are all here to-night, the whole blood-thirsty race!
It sounds like all that praying of Porphyro's has done the trick: he just happens to immediately run into our beldame-nurse lady, who's slowly wandering the halls with her cane (which is the "ivory-headed wand," by the way).
She's surprised to see him, but recognizes him, and is freaked out about him being there.
"Dude, did you not read the last stanza? A hundred swords. Count 'em. All Madeline's relatives are here tonight, so you better get out of Dodge before they decorate the walls with chopped-up bits of your heart."
Okay, so maybe she's not that sassy (she's more "palsied"—meaning frail, and kind of paralyzed—than sassy, apparently), but that's the gist of what she tells him.