wow! congrats! I'm glad you got a part like this - if your Nancy isn't being overly sexy, don't try to top her, it'd look completely wrong!
AND use your own voice for the singing, but you might want to make it more rough around the edges (she's not well brought up - let's face it
oh, and you might want to flirt a little with the gang, but be really scared when bill comes in, because you know best how he destroys Nancy's confidence, dignity, life..... and how she feels about it. You're distraught when you lose Nancy, but you don't fully comprehend that she's gone
hope that helped
EDIT: and she usually bows with Dodger although in our production, shje bowed after the Sowerberries