Romeo and Juliet might as well be a litmus test for your level of cynicism: are these crazy kids the two most romantic lovers in all of history—Bella and Edward before Bella and Edward—or are they just two hormone-crazed kids who would have bailed the first time one of them got a pimple or had a bad day at work? If you're a teenager, or ever were one, or are looking forward to being one, then you'll know that sometimes things (and people) are way more attractive if they're forbidden, especially if your parents are still making decisions for you. But that's just our cynical side coming through: Romeo and Juliet still has some of the most beautiful, passionate love poetry ever written in English. Maybe Shakespeare does want us to believe in true love, after all.
Juliet's transformation from girl to woman is reflected in the changing language she uses to talk about love.
Romeo's so-called "love" for Juliet is no different than his passion for Rosaline because Romeo is merely in love with the idea of being in love.
By reducing love to mere sexuality, the Nurse is unable to understand the strength of Juliet's feeling for Romeo. Her betrayal is rooted in this misunderstanding.