It wasn't hard to believe the truth regarding Last Lights. Sunny Jade had already experienced the supernatural abilities Wrock had, and after fighting Akiol in A World's Legacy she was keenly aware of just how different they were.
Not through a difference in skill, but rather a drive. Sunny Jade was keenly aware of why she fought so hard. Greed was her most driving factor, and even if she had redirected it somewhat she definitely still had a lot of greed. So when she fought Akiol she could sense a drive that didn't match any of the other players she crossed before.
