In Eclipse (the third Twilight instalment), Bella's (the main character) biggest fear is that Edward (her boyfriend) will leave her. That in and of itself isn't so bad. But it gets to the point where Bella can't stand to be alone. She's constantly worried and on edge. Edward had previously left Bella, saying being with him would only get her hurt (which was true) and Bella fell to peices. She wouldn't eat, only slept, never hung out with her friends, until she went to Italy to save Edward and bring him back to Forks. Bella hung out only with the Cullens (Edwards family) and thought her heart waas only big enough for Edward and all her problems would be solved once she was an immortal vampire and could spend eternity with him. On occasion, Bella would speak about Edward's soul and how the only kind of heaven she could imagine was one with Edward.
Bella dates a vampire. She hangs out with his family (all vampires) and this causes problems. Bella's unwillingness to part with Edward nearly gets herslef killed, the Cullens almost killed (all on more than one occasion)her dad's life is constantly threatened (though he doesn't know it) and her best friend Jacob (a werewolf). If Bella had let go of her idolatry and co-dependancy upon Edward, eleven lives would be safe. But Bella wont. She insits that sge simply cannot live without him.
Bella and Edward could have had a healthy relaionship (while keeping in mind that this is completely fictional) if Edward was not preimminent in her life. Had that been God; had Jesus been the one she refused to go without; had she felt so strongly at the thought of Jesus leaving her (which He never would have); then her and Edward could have had a healthy, loving relationship. Everyone, even fictional characters, were made to worship something and Bella chooses Edward.