[@Joshie]
She'll be named Riley while on Earth and I'll use 'shes' and 'hers' for simplicity's sake. She's currently her planet's equivalent to a school student. 

Her species is native to a rogue planet in the Andromeda Galaxy, hurtling into space without a sun. The species is aquatic and managed to survive under the insulation of the planet's thick crust of ice and thrive near hotspots provided from the planet's core. Eventually their technology became advanced enough that not only could they safely fare space all the way to Earth, but they managed to control and stabilize their planet's movement to force it into a stable orbit with a cold star that burns at -200 degrees fahrenheit. 

Riley was on an intergalactic class field trip to several inhabited planets. Since her species can shapeshift, they were to pose as each planets inhabitants for a time. Riley decided that humans were peculiar and fun, so she snuck off and stayed here. 

School would've been the most familiar thing for her as she was also in her planet's academic system at the time she got here. 

Her human contact would be a sheltered 8-year-old named Shannon obsessed with 80's and 90's culture who'll treat this like ET, Iron Giant and other such movies.