She would rather be killed than to hear from her lover that they no longer love her. The thought of her lover no longer loving her distresses her so much that she cannot bear to be alive if it were to ever happen.
She compares demons in her mind to her broken trust. She wants to trust his love and love him once again but the demons stop her. There is this metaphor of broken trust and trust issues. There are two devils on her shoulder - there’s no angel anymore - and she can’t keep herself from listening to them. The demons in her mind have possessed her and they won’t let her trust her lover anymore even though she wants to.