Louise and Carole are sisters. When they were younger Louise, the elder of the two sisters, would often start rows and physically bully Carole knowing that Carole would not react as she was very wary of Louise. When they were grown up, Louise’s continued mental and physical mistreatment of Carole resulted in Carole becoming increasingly withdrawn. Ultimately Carole was diagnosed by her doctor as suffering from severe depression, but she did not let Louise know this. One evening, after going out for drinks with colleagues, Louise returned in a foul mood to the flat that she rented with Carole. She mocked Carole about her unfortunate life, calling her “Mary no-mates”. Louise jabbed Carole in the chest whilst abusing her and then snatched a book from Carole’s hands and flung it across the floor. Carole begged Louise to leave her alone. Louise told Carole that she would “never be a proper woman”. Carole got up out of her chair, grabbed a crowbar that a workman had left behind that day, and smashed Louise over the head with it until Louise died.

Critically discuss the criminal liability of Carole. Support your answer with reference to relevant legal authority.
2,000 words.