Wash all fabric before you use it!!!! I know I've said this before, but red and really darks aren't the only fabrics that run.
If it were me, I'd tell the friend that it was poorly sewn, had rust from pins and that you had presumed, since it is so old, that it had been washed before. None of this is your fault and you did wonders with the damaged seams!
You have nothing to feel badly about. YOU did a good job. I'll be your friend will not fault you.
Now it looks like a real antique!!!!