What is the meaning of the final butterfly onstage?

What chapter are you referring to? 

I beleive what you're referring to is in the pats few chapters the book refers to the the characters to as butterflies. In my thought she is referring to the people in the movement as the butterflies in the story, because in earlier chapters the story said, "I dare them to lay a hand on my butterflies." This quote was referring to the sisters, he was calling them pure and important.