This dress appears in the last episode of Wives and Daughters, when Roger returns and when she visits the Towers. What lovely flowers! :-)
In each scene that we see Molly in this dress, she wears a chemisette with it, so we don't get a good view of the actual collar.
However, we see this same dress worn by Fanny in Little Dorrit. Here we get a good view of the bateau neckline:
Fanny also gives us a view of the back:Here is a long view on Molly. Now that's a long skirt! :-)
Here you can see the cuffs on the sleeves: