A.I think thats a directing choice
B. i think thats an acting choice
C. "you gave me such a fright i thought you was a ghost" subtly suggests that for a second she thought it was Benjamin Barker,(you know how when you see someone you thought youd never see again, its like seeing a ghost) thought it must be completely impossible, and ignores her first instinct, and then i think she starts to internally rediscover the possibility that it might ACTUALLY him.
D.Patti LuPone, i have noticed, tends to start to make this discovery around "my but you do like a good story, dontcha"
gotta love that sondheim
you may know what you need but to get what you want better see that you keep what you have