I finished it!
Only took staying up until 1 am because the last bit of trim fought me. But it is done, and kiddo was glowing.
I copied a gown from 1865, but changed the colors to suit the "emo Victorian vibe" kiddo was going for. The changeable taffeta glows shocking red in the sunlight, but the black undertones come out otherwise.
Got a lot of smiles walking through San Francisco this morning.