Isabella earned many bad names due to her terrible personality, and she knew about them.
Compared to being called a psycho, she hated it more when people called her "old". It was true that she had lived for ten centuries without going beyond the boundary of a level-2 wizard. Yet she would still like to avoid hearing anyone mentioning her age. She even used the look of a little girl. There was another reason. She feared that "someone" might dislike aged beings.
All in all, using "old" was a great taboo to Isabella.
Obviously, Shadow just triggered this taboo.
She was staring at Shadow with pure hatred now. It seemed Shadow also got rid of his concerns and decided to provoke the woman all-out.
"What? Want to kill me huh? Old stuff? Well, do it! What are you waiting for?"