Abby Sletten charged with assault after she struck car while using her phone . Phyllis Gordon , 24 , was killed in the May 27 collision on a North Dakota highway . Police said Sletten was viewing Facebook messages at time of accident .
Abby Sletten charged with homicide after she crashed car while using her phone . Phyllis Gordon , 89 , was killed in the May 27 collision on a North Dakota highway . Investigators say Sletten was viewing Facebook photos at time of accident .