When Catherine heard that all LS members, Kinsey and her biological father, suspected Vincent was the killer of her birth mother, Cathy did not want to believe them. She was sure that Vincent was not someone like that. After all, a fourteen-year-old teenager to kill a woman inside of strong protection made absolutely no sense.
Maybe she did blame Vincent a little for the fight that night; Cathy could also accept her brother and LS blaming Vincent, but she never thought once that Vincent was the main culprit in her mother's death.
"Because I killed your mother."
Therefore, Cathy did not expect this exclamation at all. That remark was very painful and tightened her chest. She wished she was dreaming right now.