In Shakepeare's play Romeo and Juliet, Juliet and Romeo fall instantly in love.
Though they are each a member of feuding families in Verona (the Capulets and the Montagues), they meet without knowing the other's last name. Their relationship, then, is based upon the character and qualities of the other, and not on some age-old feud in which they have little involvement.
By the time the two sweethearts realize the identity of the other, it is too late. They plan to defy convention and their family connections, and they marry secretly.
I don't get the sense that Juliet changes: she seems far removed from the politics that divide the two families. She loves Romeo, and he is devoted to her. She will do anything to avoid being wed to Paris, as her father plans, especially in that she is already married to Romeo.
When Romeo kills Juliet's cousin Tybalt, because he murders Romeo's dear friend Mercutio, Juliet is at first beside herself. She is angry with what Romeo has done. But upon reflection, she realizes that Romeo is not a part of the fighting, and that they are married: he is her husband, and Tybalt, though related, was a hothead. In the Biblical manner, she turns her back on her family and "cleaves" to her husband.
The change that I notice in Juliet with regard to those closest to her occurs with the Nurse. When the Nurse suggests that Juliet should turn her back on Romeo, Juliet's love for her husband is clearly defined once again: she is steadfast and loyal to him, and from this point, hides her plans from the other woman.
If it is a change that Juliet turns away from her family, then, yes, it is because of Romeo: Juliet loves him with all of her heart. And when the Nurse suggests she should abandon him, Juliet cuts off her relationship with the Nurse. Romeo is at the center of her existence, from the day Juliet meets and falls in love with him.