Aerin puts her mouth next to the young elf's ear and says, quietly enough not to carry any further tham him, "You know their voices?"
If his reply is affirmative, she walks back out the door and the way we came. If it's negative, she continues at the same pitch, "Go back to somewhere safe. I'll be right behind you." She'll try to peer around the door. If she sees anyone who sees her, she'll run back the way we came.
Spoiler
Hide: (1d20+1)[16]
Move Silently: (1d20+1)[20]