What was the deal with the red dress? Was it literally a relational red herring?

I assumed from the get go that Boy was actually her dog, and he was bringing the red dress because it was her/his (the dog's) favorite. This is somewhat confirmed when the dog jumps in the river--risking the Worm-Queen to save it, and the main character's frustration in that moment. Hence the "value" of that dress could have only been revealed in a final moment where it belongs to Aimee, as would the dog (the "he" that she lost in the last 7 years).

Was the ending reshot? Was this deliberate misdirection? Does anyone know the point/story behind the red dress?