I think BTML is about somebody who has been really disappointed with life and people in general, has always been treated rather badly and has shut herself up and become a ghost, a soulless puppet. She has lost hope of ever being loved and accepted as who she is, she's maybe depressed and a very dark person. Then she meets somebody, and sometimes I think she doesn't even actually meet that person, she just sees him around, learns things about him but maybe can never reach him. But he wakes something up in her, she begins to find what real world and life can be like, she's always been inexperienced and cut-off from the world, maybe more by herself than by anybody else and doesn't know what the life she threw away was really like.

The song has this kind of sad and desperate tone, I figured it was because there is romantic love involved for this person finally, but it might still not be the kind of love that she gets returned. Waking up, I think, can be understood as a growing up thing, even, you know, sexually. If nobody has ever loved you, if you've just been a shadow all your life and suddenly something like love wakes up within you, it's a very powerful experience, but also horrible if you know/fear that your feelings can never be fulfilled and returned. You know now what you're without.

Well, that's my amateur interpretation. I really love finding hidden meanings everywhere