Siren

I think something I have missed in all the commentary is the term "Vanilla", and so much of this song is about flirting (siren, coquette, "teenage flesh", etc) I would follow that logic a little further and apply the BDSM term "Vanilla" as someone who is very conventional and "tamed"

I think both the Siren (the femme fatale) and the Coquette (professional flirt) find that once they GET the attention of the man, It's disappointing because he is VANILLA, and disintegrating. Her tastes are more evolved and diverse and developed than his, he is just too "Vanilla" for her.

She was ALMOST brave And ALMOST pregnant... (And "pregnant" here doesn't need to be LITERAL, although it does also work that way symbolically as well, but it could also mean "almost beginning a new life") She slept with him and almost got trapped in his bland world... And she has more exciting pursuits to chase.

The LIE she tells is that she is interested... For a coquette isn't REALLY interested, she just flirts for attention. She doesn't ACTUALLY have interest in him, he's a momentary high for her. But she enjoys the attention so she lies... By flirting. It's her nature, it's also the nature of the SIREN, who calls men to their doom with alluring song...

Also since this song was written for the GREAT EXPECTATIONS soundtrack, I think that the characters in that film also influence this song. As Gweneth Paltrows character in that film is very much a Coquette/Siren for Ethan Hawkes character. She doesn't love him, she just enjoys the idea that he loves her as much as he does... And she is cruel to him in the process. She isn't "Holy" or even all that tremendously special to anyone BUT him... But since SHE is his obsession, she enjoys that a great deal. But in the end SHE is a little more "Vanilla" than he would hope, because she isn't a fully developed person, she was an IDEA that he was so deeply fixated upon.

The great irony is that they both had "greater expectations" of each other than either one could actually deliver... She was just an idea to him and he was just an amusement/validation of the ego for her. So the great irony is that they were both destined for disappointment in one another... She could never be his flawless paragon, and he was never what she really wanted either.

In this way the song and its association with the film is genius. Also if you listen to the soundtrack in order, Tori precedes SIREN with a song about Ethan Hawke's character's unrealistic vision of Gweneth's characters "perfection" so there is a genius to the way they both tell their own stories but her music was designed specifically to compliment the theme of the film.