Original: At the urging of the Countess, Susanna enters and she agrees to arrange to meet the Count later that night (duet: Crudel, perché finora — "Cruel girl, why until now have you allowed me to languish") since the Countess herself plans to meet the Count but disguised as Susanna.
Simplified: Susanna enters and agrees to arrange to meet the Count later that because the Countess herself plans to meet the Count but disguised as Susanna.