I'm also responding as if this applies to Act 4 Scene 1 where Juliet and Paris and the Friar are all talking in different directions.The cross-talk is highly ironic (verbal and dramatic) which gives the audience a slight emotional reprieve after the tension of the last act. It also further develops Juliet's character as a girl who insists on telling the truth but does so in such an obscure manner that no one but those already in on the secret would be able to understand her (just as she now tells Paris that she will admit she loves "him", meaning Romeo, she has also recently hinted to her mother that she wants Romeo when she told her that she's rather marry Romeo than Paris). The first  problem with Juliet's truth telling is that it is utterly ineffectual. The second problem is that no one listens to her enough to question her about the confusing parts of her speech. Juliet's mom wants her to marry Paris and so ignores Juliet's weak resistance; Paris wants to marry Juliet and ignores every point of resistance thus far. The fact that Paris actually thinks Juliet will tell the friar she loves him shows how deluded  he is; worse still, when she tells him that she'd love the back of him, he ignores her and comments instead on how her tears have "abused" her face. He sees only the surface and hears none of what lies below. We see the depth of Juliet's isolation and her utter lack of power.

You may be referring to Act 4, Scene 1 where Juliet runs into Paris at Friar Laurence's cell. She responds to him coolly and cordially, but her responses have double meanings, which is verbal irony. A sample of their conversation follows:

Paris: Do not deny to him that you love me.           

Juliet: I will confess to you that I love him.

Paris: So will ye, I am sure, that you love me.

Juliet: If I do so, it will be of more price,         Being spoke behind your back than to                your face.

Here, Paris tells Juliet not to deny her love for him, and she responds to Paris that she will tell him (Paris) that she loves "him", meaning Romeo. When Paris says he's sure Juliet will confess her love for him, she evades answering by saying if she does love him, it will be better if she tells the Friar rather than telling Paris before their wedding.

Juliet doesn't expect to run into Paris at Friar Laurence's cell, but she handles herself rather well. Paris is there talking about the wedding to the Friar, so it's ironic that Juliet has come to beg the Friar to help her out of the mess the Friar is partially responsible for since he married Romeo and Juliet. This scene also shows that Paris is a good person who truly does love Juliet.