When Juliet says this, in the garden (Act II, scene 2), she is not looking for Romeo: the English word "wherefore" means why, not where. She asks why he has to be Romeo, that is, a Montague, son of the enemy house of hers.
The use of the word in the rest of the play confirms the meaning. At the ball, Capulet asks Tybalt "wherefore" he is so enraged, that is, why he is so enraged (Act I, scene 5), and Juliet asks Romeo how he came there and "wherefore," to what end (Act II, scene 2). Right after the line, she asks him to renounce his father and refuse his name, or only to swear love, and she will no longer be a Capulet.
Then comes the most quoted phrase: "What's in a name? That which we call a rose, by any other word would smell as sweet." Juliet says that only Romeo's name is her enemy, that he would be himself even if he were not a Montague, and that the name is not part of him. She asks him to let it go and take all that she is. Romeo accepts being rebaptized as love and says he will never be Romeo again.
The name weighs because it is what makes Romeo an enemy of her house. Juliet reminds him that the orchard wall is high and that if her kinsmen see him there, the place will be his death, for being who he is.