The new order go into a new world to explore without their parents knowing, not knowing someone has followed  them. Once they realize they are lost the stranger reveals herself.

I like to think that before she joined the Order and went out with Reuben, Asha had Romeo's demenour of showing up dramaticly but mixed with Aneesah's naturally casual aproach, thus giving her her own element of surprise and making her more sly and fox like if she saw fit. She probably mellowed out as they got to know her more.