My Sunshine † Arne Johnson †

Reagan Warren wasn't a "normal" girl in any sense of the term.
First off, she was the eldest daughter of demonologists Ed and Lorraine Warren and the elder sister to Judy. That already puts a big chunk of abnormality into her life.
Secondly she shared her mother's gift of clairvoyance along with a few other abilities unique to her. Yet another reason why she would be considered a "freak" by the "normal" people.
Thirdly; her best - and really only - friend was a demon. Yes you heard it right. A demon; more specifically a demon named Malthus, better known as "Annabelle" was her only friend for several years until Arne Johnson came into her life.
Arne Johnson was about as "normal" as one could get. He had people he considered friends, was popular in school, and dated in the past. Nothing seemed un-ordinary about him.
Except his decidedly un-ordinary gift concerning the supernatural.
The two had met whilst Reagan was on a case with her parents in Arne's hometown and from there on they both found someone whom they could trust and rely on, soon the mostly-ordinary boy was joining the Warrens on jobs and growing closer to their extraordinary daughter and her demon friend.