Dear Teachers,
What I read was:
“Come here, my little mouse.”
Bianca knew enough not to come forward. “A mouse doesn’t accept invitations from a cat.” she said.
“She’s got the trim of your sails!” Lucrezia hooted with unprincipled glee.
What does it mean by “got the trim of your sails”?
Hi all potted out
I’d understand “She’s got the trim of your sails!” to mean “She understands how you think/what you’re planning (and therefore knows what to expect)”.
Since this isn’t an idiom I’d personally use, however, maybe someone else will have a different interpretation. It sounds rather British to me. It may be similar to saying “She’s got your number.”
idioms.thefreedictionary.com/have+number+on+it
Amy
.
Not British, I think, APO-- just nautical. Trimming one’s sails is getting the sails of a ship set just properly to work the wind efficiently. Getting the trim, as Yankee says, is successfully learning this, i.e. the other person’s attitude/personality/purposes.
The image could be carried even further: knowing the trim of the sails implies that one knows where the ship (or adversary) is going, what his plans are.
It is quite a nice metaphor.
.
Outstanding, MM! Your descriptive explanation is quite eloquent. 
Amy
Dear MM.
Could you please explain the meaning? 
Tom
Thanks for your replies. And, here’s another question I forgot to ask: what does it mean by “unprincipled glee”?
Unprincipled glee is joy or gaiety without any moral standards or scruples.
I am sorry to disturb you all again! 
Would anyone please answer my question???
Tom
Hi Tom
I’m kind of interested in APO myself. The only thing I know is the abbreviation for “Army Post Office”…
Amy
I think Mr Micawber just meant ‘All Potted Out’!