What is the nurse's reaction when Juliet is dead?

Juliet's nurse was in fact her wet nurse, who breastfed Juliet as a baby. She loves Juliet like a daughter, and in her introductory appearance recounts a charming memory of Juliet as a toddler, "running and waddling all about" the courtyard of the house. She says to Juliet:

Thou wast the prettiest babe that e'er I nursed:An I might live to see thee married once,I have my wish.

When Juliet falls in love with Romeo, she invites the nurse into her confidence and uses her as a go-between to arrange a meeting with Romeo without her parents' knowledge. The nurse acquiesces to Juliet's wishes, but sternly tells Romeo,

[If] ye should lead her intoa fool's paradise, as they say, it were a very grosskind of behavior.

Romeo assures the nurse his intentions towards Juliet are pure, and she agrees to help the lovers meet with Friar Laurence to be married in secret. She would rather see Juliet married to Paris, a proper gentleman, but as she grudgingly admits to Juliet,

[Romeo] is not the flower of courtesy,but, I'll warrant him, as gentle as a lamb.

After Romeo and Juliet are married, the nurse even hangs a rope ladder from Juliet's balcony so that Romeo can climb up to her room for their wedding night.
When Romeo is banished from Verona for his part in the death of Tybalt, Juliet is beside herself with grief. Her parents are completely unaware of her love for Romeo and have spent their part of the play arranging Juliet's marriage to Count Paris, which they have now decided must happen imminently. Juliet is horrified by the prospect, being already in love with and, more importantly, married to Romeo. The nurse, however, is relieved that things have worked out this way and exhorts Juliet to forget Romeo and marry the much more suitable Paris.
Juliet, in despair, flees to Friar Laurence in hope of some advice. Friar Laurence devises the complex fake-suicide plan to reunite Juliet with Romeo and gives Juliet the poison needed to put her in a death-like sleep. Juliet takes the poison that very night, and when the nurse goes to wake her the next morning, she finds Juliet apparently dead by suicide. Because she knows the truth of Juliet's love for Romeo and opposition to the proposed marriage to Paris, she feels complicit in Juliet's death and in anguished guilt, she cries out:

O woe! O woful, woful, woful day!Most lamentable day, most woful day,That ever, ever, I did yet behold!O day! O day! O day! O hateful day!Never was seen so black a day as this:O woful day, O woful day!