She's Mistaken You For Her Friend/Crush, Red!

Yellow is quite naïve and acts very much like a little child. She hates it when Pokémon are injured, hers or her opponent's, and has developed a style of battle in which neither her nor her opponent's Pokémon are hurt unless it is absolutely necessary. Despite her childlike nature, she can be very serious when people and places she cares about are threatened, shes 25 years old despite this.