Ainsley had never personally felt the process of transforming her body from a human body to another race's body.
Back then, even when Ainsley became a blood clan, she was in the state of being unconscious.
The only thing she experienced fully was the process of growing wings, and that alone was already so painful.
Now, Ainsley was sober, and she had to fully experience the body transformation from a human body to a demon body.
People might ask why Ainsley didn't enter her blood clan mode before transforming to demon form so that it would not be so painful.
However, it was precisely the opposite. If Ainsley were in her blood clan mode before she became a demon, the body of the blood clan would have to be 'smashed' or 'reset' before the demon body could be formed.
Ainsley's human body had already been tempered due to the resurrection, so she should still be able to bear the pain when transforming to a demon body from a human body.