The song plays on the saying "You took the words right out of my mouth" i.e. saying something right before the next person was going to say the same thing, in this case "I love you". In this case making it both figuratively (she said "I love you" in the moment before he did) and "literally" (she did so by actually taking the words out of his mouth while kissing him).
The song plays on the saying "You took the words right out of my mouth" i.e. saying something right before the next person was going to say the same thing, in this case "I love you". In this case making it both figuratively (she said "I love you" in the moment before he did) and "literally" (she did so by actually taking the words out of his mouth while kissing him).