He proposes a way (convoluted and dangerous to be sure) for her to escape and go to Romeo in Mantua. This is obviously a better choice than suicide, but suicide is never far from her mind.
she would kill herself
Friar Lawrence married Romeo and Juliet in his cell.
She threatens to kill herself. Well, the friar reasons, if she is prepared to really die, she should be prepared to pretend to be dead.
In Act IV, scene I of Romeo and Juliet, Juliet threatens to stab herself if Friar Lawrence does not help her.
He's sure that Juliet will accept his plan because Juliet has just vowed that she would rather kill herself than have to marry Paris and he is offering her a way to get out of marrying Paris that isn't as scary as killing herself.
Romeo, Juliet, and Friar Lawrence are in Friar Lawrence's cell.
Romeo goes to friar Lawrence about marrying Juliet
She is confused and desperate because she does not know what to do and was going to kill herself if Friar Lawrence did not come up with a plan to help her.
She was anxious and desperate. If the Friar had not thought of a plan her intent was to kill herself, right there.
she's killing herself with a sword or a knife because her husband was death
The Nurse and Friar Lawrence knew about it before anyone else because the Friar performed the marriage and the Nurse was Juliet's close confidant so she told her everything.
Friar Laurence performs the marriage. Hope this helps! :)