During the Renaissance, the role of nursemaid to the aristocratic children was often played by poor maiden relatives taken in by their family. In such a position, the Nurse has come to love Juliet as a daughter and is very proud of her. When Romeo approaches her in Act I and asks who Juliet's mother is, the Nurse claims that role practically for herself:
Her mother is the lady of the house
And a good lady, and a wise and virtuous.
I nurs'd her daughter that you talk'd withal.
I tell you, he that can lay hold of her
Shall have the chinks. (1.5.119-124))
In keeping with her close bond with Juliet, the Nurse arranges Juliet's and Romeo's nuptial night together before he is banished. Thus, she is willing to betray her employer in order to ensure Juliet's happiness. It is only after Romeo's banishment that the Nurse fails in her loyalties as she counsels Juliet to renounce her marriage to Romeo and marry Paris. However, she still has Juliet's happiness in mind, believing that Romeo will never return.
However, prior to this, when Lord Capulet insists that Juliet marry Paris, the Nurse does come to her defense:
God in heaven, bless her!
You are to blame to rate her so. (3.5.173)
That the Nurse loves Juliet dearly is evidenced in the final scene of Act IV as the Nurse is reduced in grief to a parody of herself as she tries to waken Juliet, speaking nonsensically about sex:
Go, you cot-quean, go,
Get you to bed! Faith, you'll be sick to-morrow
For this night's watching. (4.4.6-8)