She probably didn't. There was only so much that they knew and a lot of that stuff about the chemical in Bree that extends life, she wasn't around to hear. She was buisy advertising for the Hymn of One. She probably knew that the ceremony was important but she probably didn't know what it was until it was too late to back out. Plus, at the beginning, her parents didn't tell her anything. Emma's getting a good head-up that Bree didn't get. She might just live.