I still don't get the meaning (sorry, I have a shallow knowledge of general relativity). Literally "You are the Einstein tensor in my Einstein equation". Maybe, "You are the solution in my equation"?
Let's see... If G = "universal gravitational constant" [http://en.wikipedia.org/wiki/Gravitational_constant], and "a solution of the Einstein field equation" = spacetime, then "you are the G in my spacetime" could mean "you are the one I'm attracted to", aka "I love you", I guess?