Demon wars

Earth has been in an never ending war with aliens since the year 2666. The war is known as the Abyss war the black hole of a war that just keeps taking, soldiers, recourses... hope. The people of Earth have now lost any hope of the war coming to an end, so they live like every day is their last which in all honesty could actually be true. The government also known as the Milky Way Federation or most commonly used MWF has put together an army of epic proportions. 1 out of 50 sixteen year olds get chosen to become an Interstellar Soldier, they get sent to a school in space to train to fight aliens for four years before going out onto the battle field. But it isn't as easy as it sounds, those chosen few get put through hell... literally. If they survive they become super human... no that's wrong... they become Demons.
Our hero, Mara Dragoon, has the worst luck ever because she has been chosen to become an Interstellar Soldier at the worst possible time in the war, a heavy fate has been thrust into her lap before she can do anything leaving her with nothing but lost hope.