The Nurse and the Friar both engage in forms of rebellion in Act II. What kind of rebellion do they embrace? What is their motivation for breaking...

I assume you are referring to Act II when Friar Lawrence agrees to marry Romeo to Juliet and the Nurse becomes Juliet's accomplice in arranging the marriage. 

The social order in Verona at this time is one of conflict. The Montagues and Capulets are engaged in a bitter feud as evidenced by the brawl in Act I, Scene 1. Despite the differences between their families, Romeo and Juliet fall in love. In Act II, scene...

I assume you are referring to Act II when Friar Lawrence agrees to marry Romeo to Juliet and the Nurse becomes Juliet's accomplice in arranging the marriage. 

The social order in Verona at this time is one of conflict. The Montagues and Capulets are engaged in a bitter feud as evidenced by the brawl in Act I, Scene 1. Despite the differences between their families, Romeo and Juliet fall in love. In Act II, scene 2, Romeo proposes and Juliet accepts. They never really discuss the opposition their parents will have but instead launch into a secret relationship and only inform Friar Lawrence and the Nurse of their love.

At first the Friar is quite skeptical of Romeo's newly announced love for Juliet. Only the day before the boy had been in love with another girl. Romeo assures the Friar that his love for the daughter of Capulet is true. Obviously the Friar, being a man of peace, disapproves of the feud and Romeo's request provides him with a chance to bring the bloodshed to an end. Therefore, he rebels against the social order and agrees to marry Romeo to Juliet. He believes it could be a vehicle to finally stop the rivalry. He says,

But come, young waverer, come, go with me.
In one respect I’ll thy assistant be,
For this alliance may so happy prove
To turn your households’ rancor to pure love.

The Nurse's motives for going along with Juliet are less noble. She dearly loves the girl and wants more than anything for her to be happy. In Act 1, scene 3 she says,

Peace. I have done. God mark thee to his grace,
Thou wast the prettiest babe that e’er I nursed.
An I might live to see thee married once,
I have my wish.

The Nurse originally believes Juliet might be married to Count Paris, but when the girl reveals her love for Romeo, the Nurse is excited and goes along with the marriage. She acts as Juliet's messenger in discovering Romeo's plan for the wedding. In Act II, scene 5, she praises Romeo:

Though his face be better than any man’s, yet his leg
excels all men’s, and for a hand and a foot and a
body, though they be not to be talked on, yet they
are past compare. He is not the flower of courtesy,
but I’ll warrant him as gentle as a lamb.

She even agrees to procure a rope ladder so Romeo may climb into Juliet's bedroom for the honeymoon. Ultimately, the Nurse just wants Juliet to be happy, and if that happiness is with a son of Montague, she is perfectly willing to accept it and rebel against the social order.