This is an interesting concept. I certainly think that Juliet does find herself in a condition that sets her apart from others. At the very start of the play, Romeo is surrounded by friends who are trying to encourage him to be happy and content. Yet, Juliet is seen as almost "an island" in Verona. The very first scene where she is speaking with her mother is a part of this. The entire discussion about Juliet's future is never really discussed with her, but rather between the Nurse and Lady Capulet. Juliet is more on the outside and her responses about pleasing her parents is a part of this. When she falls in love with Romeo, she seems a bit distant as she is more concerned with the practical implications of their relationship than Romeo, who is simply immersed in his infatuation for her. Juliet is not shown to have much in way of any confidence in the drama. The Nurse might be her closest, but there is a guardedness in the manner in which Juliet interacts with her. Juliet's condition of aloneness is most evident in Act III, Sc. 5, when the conflict with her parents reaches such a point where she is disowned by her father and rejected by her mother if she does not follow their directives. I think that in this, one can see how alone Juliet actually is, something that might be temporarily fixed with her love for Romeo, but might be more of an element of her personality that is embedded.
Throughout the play Juliet isnt able to basically speak her mind. Her parents are in total control of her life, and she really didnt have any friends from what one could tell within that short play. Now she was shown to be isolated from her lack of friends and inability to speak her mind.
Keep in mind, her engagement to Paris is arranged by her parents, and her only friends, or rather acquaintances were Romeo, Friar Lawrence, Tybalt(who was killed), and Nurse. Now remember most of these are simply family or church figures. Only one is a true friend, and he is hated by her family, and she must keep him a secret :)
(Read the play last year in honors english. Its an easy topic to understand if you have a decent teacher explaining it.)