In Episode 6, "The Smell of Enchanting Blood," we learn a lot about the changes Tamayo has gone through as a demon. Though we later discover she started out violent and even ate her own family, Tamayo has managed to alter her physiology so she doesn't have to eat people to survive. She tells Tanjiro that she instead buys and drinks blood from people in poverty — though never enough to impair anyone — telling them she'll use it in her medical practice. Tamayo's dedication to becoming a "better" demon shows just how much she cares about humans and wants to defeat Kibutsuji.
Not only did she change her physical needs, but she also managed to remove Kibutsuji's curse. Since Kibutsuji is the Demon King, he has extreme power over most of the demon population — except for Tamayo. This gives her the freedom to rise against him, and also shows how powerful she truly is, since she was able to break free of Kibutsuji's grasp.
