The little girl who was seated before the mirror had watched everything even when 'Yvonne' in the dream had failed to do so.
Since Howard had covered her eyes, the young miss had not witnessed what the little girl who had conjured this dream had been able to catch sight of.
Therefore, Yvonne had a better understanding of what had taken place in the brief moments that her counterpart in the dream had her view blocked.
In that dream she had seen, Yvonne could see things beyond what older 'Yvonne' was capable of.
Thus she had a clear view of what had taken place while Howard had covered his little sister's eyes.
The moment the pair of brother and sister had entered the room, Yvonne was busy admiring the large arched glass door but Howard's eyes had sought out the one they had come over to meet.
'Yvonne' and Topher's first real conversation took place here. Wonder where that leads them~