This was like another version of the "Guess Which Hand" game Kain had shown her, but instead of two hands and a stone, it was three bowls and a small ball.
Mera realized that the biggest difference between this game and "Guess Which Hand" was the item-hiding stage. In the "Guess Which Hand" game, Kain would put his hands behind his back to choose which hand to place the stone in, forcing Mera to rely on "clues" he provided afterward to guess which hand held the stone. And those clues could be completely faked by Kain.
In this girl's game, the process of hiding the ball in the bowl was done in the open, in front of Mera. The clues the girl left were also impossible to fake because Mera had an objective basis to compare them against. Thus, Mera was confident that she could use the girl's gaze to determine which bowl the ball was in without fear of being deceived as she was with Kain.
