There's been a great deal of discussion on the Board re mourning before, but I don't think one can state categorically that a father needed to be mourned 12-18 months - that's more like a Victorian dictum rather than a Georgian/Regency rule.

Six months was an acceptable maximum to mourn a parent in polite society; those of the lower orders probably didn't bother with the luxury of a special wardrobe for mourning. Even Jane Fairfax in Emma comments that her wedding to Frank will be delayed only for six months when his stepmother dies.

And yes, my biggest quibble is with the lack of distinguishable mourning gowns in the beginning of the movie. Elinor and Marianne should at the barest minimum be wearing black gloves, ditto Margaret. Full black for the first three weeks or so, then half mourning for the remainder, which is grey and a mixture of black and white. Lavender was never a half mourning colour during this time, that's another Victorian convention.

And Kaarin, I believe that the robe a l'anglaise had nearly disappeared by 1795; that long bodice with the back en fourreau is not seen at all in the fashion plates after 1798. It's been replaced by the open front robe and petticoat combination, with a short waist. (That's the 1795 peach robe from Waugh; there's a nice photograph of the original dress at the Metropolitan in the "Age of Napoleon" book put out by the museum.)

Louisa
Mistress of the Garderobe