In episode 12 of The Promised Neverland. Isabella tells Phil, the smartest among the 4 year olds, that the other kids escaped safely and he did not need to worry. Did she know that Phil knows everything about the farm?
And if she did, did she suspect everyone below 4 years old?
She did suspect Phil but then after looking for the situation she concluded that the younger kids didn't know anything. (chapter 35).
So why did she tell Phil everyone has escaped safely? That's because she already admitted her defeat (chapter 37), and with that, she had nothing to lose anymore.
But ultimately, it's because from the bottom of her heart, she actually loves them and didn't want Phil to worry about them
Once Isabella understood Ray and Emma's whole plan, she was able to guess that Phil was sent to distract her. Hence why she was fully honest with him : she knew he was aware of the plantation's secret and she had no more reasons to stay deceitful.
Since Phil was just leading around the other younger children to deceive Isabella, she has no reason, on the other hand, to believe they are also aware of the plantation's true nature.
