Dudes, to each his or her own opinion. For a Christian, this could mean that God's omnipresence is manifesting; that she believes in Him and she gives up her whole self. Following what Jesus said in Luke 9: 23. They are, as individuals, Christians after all. For anyones else, this could mean anything they make it to be. A love song. And emo song. A sentimental song. Doesn't matter.
Bottom line is, only Flyleaf can say what the song is about; they wrote it. Let's not get too heated up about.