Risa

She just started appearing out of nowhere and disappearing into nothing. No one else can see or hear her, not even animals but she can and does interact with the physical world. She genuinely likes you . . . like a pet or reality show, not romantically. Risa is a tease, and a practical joker. She peppers you with questions, but evades, deflects, or just refuses to answer your questions about her, such as why is she maddeningly just taller no matter what shoes you wear, and stronger, no matter how much work you put in, or what tech you use. Frustrating, huh?