The librarian removed herself out of the room and into the real library where the search over the subject started. The mare didn't want the filly to come in there on purpose and obvious reasons. All for the simple fact she didn't want to clean the whole area up again and given how Spike was on vacation, she had to do it alone. The young Sweetie could understand it and she didn't even question it, much like the rules of staying with and coming over to her sister.