Elizabeth North didn't want Mellie to give on her Presidential Campaign; she may not like people but she didn't want Cyrus Beene to become the new President; she event went on TV with Abby Whelan to tell the American people that Cyrus was a liar and he didn't deserve to become President. To try and help Mellie become President, Elizabeth was working with Samantha Ruland and Theodore Peus, they mey Mellie in her office to discuss to offer to help Mellie become President.
Elizabeth was killed by Samantha Ruland when Mellie refused to help Theodore Peus become the new President of The United States of America. Peus told Mellie that she was either going to become President or they would kill her and her children; in shock and having no other reason Mellie said "yes".
Mellie then called Olivia Pope to her office (without tell her what had happened on the phone), Jake Ballard was at hand to tell Mellie that he was going to help her and the situation was just a bump on the road.