These are so beautiful!
I'm so tempted to make a replica of one now, aha.
I just wanted to add that I know a lot of people will use a vinegar soak to set red/pink dye (which is usually the most prone to bleeding) into fabric before washing it so it won't bleed onto other clothing or white trimmings, etc. It's possible that's what some mother may have tried to do with your cape,
mlp4me, and it didn't go so well! My own mother does this all the time (I do as well), and it usually works great, but I've never tried it on silk/satin. It would certainly explain the vinegar smell!