I don't think there are four quotes which "blame" the nurse. But here are four quotes which point to the Nurse's role in the tragedy of Romeo and Juliet - and perhaps help lead to their eventual death.
In order. The Nurse, even before Juliet has met Romeo, encourages her to enjoy herself and meet boys, despite her young age:
It's no surprise then that Juliet tells the Nurse about Romeo and uses her as a messenger. The Nurse is explicit about encouraging Juliet to have sex:
Then hie you hence to Friar Laurence' cell;
There stays a husband to make you a wife...
I am the drudge and toil in your delight,
But you shall bear the burden soon at night.
Go; I'll to dinner: hie you to the cell.
And, even once Romeo has murdered Tybalt, the Nurse is risking the law to conspire with Friar Laurence to get the two people together:
Yet, after all the Nurse's encouragement, she eventually betrays Juliet, giving up on Romeo, and advising her to marry Paris. She does do the honorable thing (as a member of Capulet's staff!) eventually, but it's too late to have any influence:
I think it best you married with the county.
O, he's a lovely gentleman!
Romeo's a dishclout to him: an eagle, madam,
Hath not so green, so quick, so fair an eye
As Paris hath.