I've been thinking about this episode and one thing that keeps striking out at me was when they were in the Shadow Proclamation and the woman noticed the bug on Donna's back. I hope that scene isn't forgotten in the finale.
For what it's worth...
This was brought up earlier in the thread. I went back to see exactly what was said in that scene. What the woman said to Donna was "There was something on your back".
I think the more important line in that scene was her next line. "You are something new". What any of that means only RTD knows at this point.