I would encourage it interpreted however you like. There isn't a rule on it but I offer the following further thoughts:
The uncertainty and certainty aspect is what happened to Lilly, because that is what she's about in my head. The same thing wont necessarily happen to another though would happen more to children who don't really know who they are yet.
Also, it is not changing a person's mind, but something a little more subtle then that. I envision it more like 'rebooting' a person's sense of self and attaching onto whatever it finds. All those forces were in Lilly to start with, just given voice. But because she is a child, there are so many different aspects to her, the net effect would eventually be to cancel out and retain a democracy within mind restoring 'balance'.
Now it has not been established, but suppose Tiffany had exposure to the enemy and thus explaining her first change. She always had this edge to her and the forces 'grabbed' onto one particular sense of self overriding all others. Other voices were mitigated, because she is older, so it became 'self'.
Same exposure, two different reactions. And it can be very unpredictable in just where it could go. On Lucas, anything could happen.
I know this is horribly complicated metaphysics, but I thought it an interesting direction to go on. Any thoughts?
