Zentmeister
I think she (S’aleth) will somehow survive this onslaught alebeit being the lone survivor and then turn her hatred to Erich who did not inform her any of this while knowing and in the process becoming a villain. She will return in next 200-300 chapters when Erich will be on his process of building his empire. After the fight she will eventually come to know the truth and will regret her decision [Well That My Theory].
That is exactly what happened,i mean, the GSE stated goals was to use them as meat shields for the enemy. that's why she's stupid for even falling in love with a soldier who was actively subjugating her own people/nation. Her people were right to fight back. there is zero point in even fighting the enemy anymore, they are better off trying to flee into other Nations that might accept them as refugees.