What impression does Shakespeare give of the nurse in act 2, scene 5?

Juliet's nurse is a comic relief character in Romeo and Juliet, but she also plays in important part in helping Juliet to marry her true love, Romeo. In act II, scene 5, the nurse tells Juliet about Friar Lawrence's plan to marry the two lovers in secret and that she must go to the friar to be wed.
The nurse doesn't tell Juliet this news immediately—instead, she toys with Juliet, dodging her constant questions about Romeo and complaining about her body aching. This is an example of the nurse's playful personality coming through—the nurse knows all Juliet cares about right now is Romeo, and she uses that knowledge to mess with her a bit.
We also see a dirty side to the nurse with this line:

I must another way, / To fetch a ladder by the which your love / Must climb a bird's nest soon when it is dark (2.5.65-67)

Meaning that Romeo will climb into Juliet's chambers at night and sleep with her. Again, this shows the nurse making light of Juliet's love for Romeo; while the nurse eventually does tell Juliet what she wants to hear, she lightly teases Juliet first.