Shared Trauma (Steve Harrington)

Emilie Henderson was damaged. Everyone knew what happened to her. Or at least, they knew enough. When she was thirteen she went camping with her father and they both went missing for nearly two weeks until Emilie was found barely alive with deep wounds from an unknown origin and her father was found with his eyes caved in and his bones cracked.

She was in a coma for thirteen weeks when she came back she had no memory of what happened. Doctors said the trauma was so great that the young girl blocked it out. But ever since then, she kept having nightmares of a place. Like this world but cold and dark. She lived with the Byers as she became friends with Jonathan and was like a daughter to Joyce until her brother and mother were able to move to Hawkins with her due to complications.

She's now known at the traumatized girl of Hawkins High with the freak brother, yet somehow she is Steve "The Hair" Harrington's best friend albeit their relationship has gotten rocky. She deals with normal things along with her nightmares and trauma-school, bullies, insecurities, and being in love with her best friend.
But when Will Byers goes missing and odd occurrences start happening, Emilie's memories start coming back.