who is anna angel?

I've finished P2 three times already, and when I was talking to anna for the last time on day 12 I realized that even after three playthroughs I can't remember exactly where I met her, or how relevant she is to the plot, all i remember is that she worked at a circus, said the plague was caused by her, and I had to look for a sprindle to trade it for a heart, she just feels out of place for a bound character