Her blog explains the process and the results, and it is well worth the read in full. An excerpt:
One girl had the idea to have protestors as a consistent element all the way across the mural, but changing according to whoever they were next to. For example, the protestors next to Chavez would be holding signs that said different things than the protestors next to Susan B. Anthony. Genius!!
More about the artist's business here.
Since it is International Women's Day, here is a close-up of the Susan B. Anthony portion: