Mariana

 was the wife of Mikhail and the mother of Pris.

Mariana and her family were part of a colony ship, the Amandala, that was heading for Galaxy Eight. However, an emergency on the ship caused core damage, and in order to prevent a core rupture, the Eighth Doctor shunted the energy away. This had the effect of creating an EM pulse, which killed Mariana and everyone else on board except Mikhail. (PROSE: Reversal of Fortune)