She was a counselor at the summer camp he went to, and we can infer he had some infatuation with her, hence the vial of her blood. Jordan's got some fantasy fetish, that Emily is so beautiful that he can't touch her. I believe Lumen said that there was always one guy who just stood there and watched "The Watch Guy". . . "tick tick tick, that's the sound of your life running out". That was Jordan. For whatever reason, he feels he's not worthy of touching her or something, why he took Emily's hand off his, why he just stood there during the torture of those girls.
She has some Stockholm Syndrome or something, so she feels like she owes him for keeping her alive. All in all, they're both completely messed up in the head, so it's probably good that it's hard to understand their relationship, haha.