Anna Lagwinowicz and her uncle Tadevsz Dmytryszyn are accused of dumping the body of Catherine Wells-Burr, 23, in her Ford car before setting it alight.
Ms Lagwinowicz, and Mr Dmytryszyn, 38, are accused of driving the business analyst's body to a nearby roadside, placing her in the driver seat of her red Ford Focus and setting the car alight with petrol.