Where is it evident that Laura Wishart was raped and got pregnant?

Laura Wishart is Eliza's older sister and Jasper's girlfriend, who is found dead by Jasper and Charlie at the beginning of the novel. Jasper and Laura planned on leaving Corrigan together. Like her sister, Laura is described as calm, peaceful and intelligent. It is later revealed that Laura committed suicide and that she was pregnant with the child of her father, who had sexually and physically abused her.