Ainsley's charm ability was indeed too difficult to be detected, especially when she used it bit by bit to avoid the machine's detection.
Experts should actually be able to feel whether they were being targeted or not, or whether someone used abilities on them, but charm ability was too difficult to sense.
After all, before the user of the charm ability used it to command others to do something for them, most people, including experts, would not be able to feel the change in their emotions carefully.
As long as the ability user remained silent, the charm ability could work silently, waiting in the dark.
Before Ainsley made the irregular tamer guild, even the best charm ability users had a limited way of thinking, and they subconsciously only used their appearances or voices as the medium of their charm ability.