The name 'mimicry' made Aria want to use her power to eradicate it. She had encountered the mimicry twice, and neither had good recollections.
The first was when she brought a cat home, which was a disguised mimicry. The second was a mimicry disguised as her uncle and injured Lyod and Khan.
From then on, Aria considered mimicry a disgusting creature that shouldn't exist. Everyone believed hybrids were dangerous and shouldn't be born into this world. But according to Aria, it should be mimicry was never born into this world.
Aria should have guessed it. The capability that could change one's appearance, as well as her aura, came from mimicry. She was so stupid that she couldn't realize it and assumed that Regine had been the one who had changed her appearance.
And now… the mimicry she least wanted to see again appeared in front of her with Atha's face and head down.