Lives were lost as a direct consequence of her actions.
She didn't set out to kill them, so it's not murder but if she hadn't acted the way she did-her actions-then four souls would be alive today. She showed no remorse-she lied and tried to blame a dead colleague.
I imagine that's why she got 2 years six months for each life that was lost-which seems pretty lenient to me.
Four people will no longer feel the sun on their back, no longer laugh, no longer see their loved one, no longer cry, no longer sleep, no longer breathe because of her actions. She condemned them to darkness.
I think the sentence should have reflected that and been 5 years for each life which is still lenient.