As far as I know, she's never performed the song live. I'd definitely love to hear it, although I don't think anything will ever beat Pierre Marchand's production on it.
Definitely love the line "Love is what you believe it is" from the demo (you can hear this on the album version as the very end if you crank your speakers). This has been a very meaningful song for me. I'm getting that line tattooed on my arm in May.
I started a "Let's talk about..." thread a few months ago. Tons of speculation of meaning, and I think the demo may have been posted there as well, if you don't have it.
http://ledge.fleetwoodmac.net/showthread.php?t=41114