After talking to Ritsu about the truth of their world, Aria and Shogo ask him to lend them his aid. Later Shinohara Mifue and Morita Naruko, who also started to notice the incongruities in their world like Ritsu, visit the music prep room as well.
While others are talking about people being "spirited away" on the gossiper, Tomoe Kotaru dashes into the room claiming he can no longer reach his friend who went into the library...
As you've surmised, 
this world was created by μ.
كما حزرت، صُنع هذا العالم بواسطة ميو
Como sospechas,
este mundo fue creado por μ.
Como sospechabas,
este mundo fue creado por μ.
Tu as tout à fait raison.
µ a créé ce monde.
Proprio come hai dedotto tu, 
questo mondo è stato creato da μ.
Como você deve ter suposto,
este mundo foi criado pela μ.
Как ты и догадался, этот мир создала Мю.