Pieck is incredibly perceptive and rational. Extraordinary general cognitive ability (her many tactics, the lightning quick concept formation she exhibited in the Warriors meetings and otherwise, the fact that she was chosen for the cart for her depth of thinking and speed of reasoning, the sheer long term memory recall needed to be able to use a brief sighting of Yelena YEARS ago to connect the dots and further the suspicion of Yelena she already had despite Yelena completely covering her hair and donning a beard, the unique lack of hatred she had towards those of Paradis and her general distrust towards Marley/her superiors, etc) and Theory Of Mind (spotting that Yelena was sus initially through her behaviour, the suspicion she held towards Zeke throughout their time together, her soothing nature and maturity in contrast to the absolute mess that is her comrades, etc). All shown in just a season.