She is a kind-hearted trainer, but is constantly manipulated by her Gothita. Seeing her Gothita having crush on Ash's Scraggy, she challenged Ash to a battle with the condition that if she won, she would take Scraggy for Gothita. However Ash managed to defeat her Mandibuzz and thus saved his Scraggy.
Katharine's Gothita is very bossy which really liked Scraggy. Due to that crush, her trainer challenged Ash to battle.