Watermelon-ie
Aleena doesn't like school. It's too loud, too much, too- too school. She doesn't like it, but she likes it better than the double in her head that keeps talking to her, whispering in her ear and shifting her vision. School is annoying, but getting transported to another world? Even more so.
Rosemary doesn't mind school. She's got friends, decent teachers, a nice image; she's average, but she likes it. Her grades aren't picture perfect, but those become the least of her worries when someone from her friend group goes missing.
Aleena's memories struggles to keep up with all the new experiences in the second world, while Rosemary and those she left behind are scrambling for clues on where to find the girl. Head detective Melanie finds clues, but no one knows how. They can't stop to think about why Melanie has photos of a guy last seen with Aleena, or how she remembered the entire route Aleena takes to school.
No one was supposed to notice Aleena.
No one was supposed to notice her gone.