She started the war in order to make as much casualties as possible to feed the Maw and the Jailer which in itself an atrocity.
And no, in Elegy she even mentions how destruction of Teldrassil and War of Thorns will destroy night elves as a people, or at least as a nation.
Also writers went on a long tangent to explain how night elven population was first forced to leave their scattered settlements around Kalimdor due to Horde’s aggression and then mostly settled in Ashenvale. Then horde smashed through Asehnvale, either killing then or forcing them to flee to Teldrassil. Then horde torched Teldrasssil hence killing the majority of night elves on Kalimdor.
Its like herding entire village into a barn or a church and then burning it, but on a bigger scale.