After Ash finished explaining the effect of the Flash Tail, Vishi showed a very subtle expression.
"Weren't you with me the entire time?" Vishi pondered, "When did you secretly cut the White Bull's tail? ...Wait, there was indeed a period when we were separated, could it be that this was..."
"This isn't Nia's tail!" As soon as Ash saw Vishi's expression, he knew what she was thinking. He said irritably, "Don't overthink it. This thing has the same origin as your ruby chain. So you understand now, right?"
During the second Angel Hunt, the only time Ash and Vishi parted ways was when each got trapped in the ruins. Ash suddenly pulled out a loot item she had never seen before, so it's no wonder Vishi linked it to something falling off Nia.
"I don't understand." Vishi shook her head, "You never told me how the ruby chain came about."
"Exactly," Ash said, "I won't tell you, so thinking about it is a waste."
