I think this song is about how we fall in love with the idea of someone and confuse that with the reality of who that person really is - which may effectively defy that idea. She's saying "Don't invent me, 'til you need me" - note that she uses the word 'need' as opposed to 'want' which is most commonly used in love songs. "I want you, I want to be with you", etc. She is not denying that there's an element of falsehood involved with the notion of 'inventing' someone, but she would rather be assured that the ideal stems from this person 'needing' her.
I think this song is about how we fall in love with the idea of someone and confuse that with the reality of who that person really is - which may effectively defy that idea. She's saying "Don't invent me, 'til you need me" - note that she uses the word 'need' as opposed to 'want' which is most commonly used in love songs. "I want you, I want to be with you", etc. She is not denying that there's an element of falsehood involved with the notion of 'inventing' someone, but she would rather be assured that the ideal stems from this person 'needing' her.