The girls just doesn't feel like she deserves the guy. She wants to be everything that he loves in women, which seems to be beyond mortal. His world seems perfect, and all she wants to do is be a part of it. She compares herself to Lucifer, the epitome of all that is NOT good, to prove that it's possible for someone as imperfect as her to be able to fit in his life.
The girls just doesn't feel like she deserves the guy. She wants to be everything that he loves in women, which seems to be beyond mortal. His world seems perfect, and all she wants to do is be a part of it. She compares herself to Lucifer, the epitome of all that is NOT good, to prove that it's possible for someone as imperfect as her to be able to fit in his life.