I have seen Leslie twice now, and have a pretty good idea of what I need to do. There were several problems with the mockup that were evident the first time she tried it on; The bodice front as draped may have looked good on the padded dummy, but not so good in person. On person. Whatever. Also, she has been going to the gym; in general this is good (less fabric needed to go around a smaller person, better lines, etc), but it does mean that the old measurements and the padding on the dressform are moot. I had put in side bust darts, as well as two underbust darts at each side, which had worked on the dressform, but looked very strange indeed when we put the mockup on her. The mock was longer-waisted than it needed to be, and I had added so much for hem allowance that it was weighing the dress down and being generally distracting. So, I took the muslin home, pulled the zipper and side seams out, pulled the bodice off and picked out the bust darts. I interfaced one layer of the bodice front to help keep it from stretching. I put one of the underbust darts in on each side, and then reattached the bodice to the skirt along the appropriate lines, front and back. I pinned in the other underbust dart and carried it along into the skirt. I left the side seams open to help with fitting. I also cut off about 3 extra inches of hem allowance.
In general I was able to move the pins around enough to make the mock fit. The only other thing I need to do is raise the back neckline about 1 inch; I thought when I made the muslin that it would hit just at the base of the back of the neck, but it seems to ride low. The front of the skirt is also a bit wide, so I need to narrow it to make it look a bit sleeker. We're not going to do the apron, or the pleated waistline trim; she suggested a line of piping there instead. I also need to take a look at the 6 hour Pride and Predjudice so I can drape a spencer. I think the waist on this dress is lower than the ones in the movie, but I think it might be adaptable with a little finagling.