Measure for Measure Marriage Quotes

How we cite our quotes: (Act.Scene.Line). Line numbers correspond to the Riverside edition.

Quote #10

DUKE
Dear Isabel,
I have a motion much imports your good,
Whereto if you'll a willing ear incline,
What's mine is yours and what is yours is mine.—
So, bring us to our palace, where we'll show
What's yet behind that's meet you all should know. (5.1.608-613)

Again, when the Duke mentions marrying Isabella, our girl is completely silent.  Is this because Isabella still has ambitions to be a nun and doesn't want anything to do with the Duke?  Or, has Isabella changed her mind about sex and marriage?  How would you play this scene if you were an actor?