When Juliet asks "wherefore art thou Romeo?" she knows exactly where he is. She's looking at him and talking to him and immediately after that, she starts talking about how he should change his name or she should change hers. If you actually read the words instead of just moving your lips and making sound come out because your English teacher is watching, then it's pretty obvious she's talking about "Why did the man I love have to be from the family that is the enemy of my family? Names aren't that important, are they? Roses, sweet, etc."