Ms Lagwinowicz is said to have joined Mr Dmytryszyn in dumping Miss Wells-Burr's body in her red Ford Focus before setting fire to the car at about 06:00.
Alonso, a two-time drivers' champions, made first appearance of preseason in Catalunya on Tuesday, but Vettel remains focus on ensuring Red Bull arrive at the season-opening Australian Grand Prix on March 17 in the best possible shape.
Miss Wells-Burr, who graduated from Bath Spa University with a first-class degree, was discovered by fire crews in her red Ford Focus in a field in Ashill.