How does Juliet mislead her mother in this act three?

In Act Three, Scene Four of Romeo and Juliet, Juliet does not actually mislead her mother. When asked if she saw Tybalt in a vision last night, Juliet replies truthfully that she did not - "Yea, noise? then I'll be brief. O happy dagger!/ This is thy sheath (takes ROMEO's dagger); there rust, and let be blood forever/ But Romeo's and mine"