The specific mechanics behind the respawn system is that Ariane rewrites a random nearby LSTR unit to have Elster's memories. That's why there's random bodies left behind despite time looping weirdness, especially in the elevator shaft where Adler pushes you.
Alina Seo DID exist, but the original her died decades ago. Then she gets revived as a sorta-ghost by Ariane due to memory shenanigans. And then metamorphosis'd into Ariane anyway. So Alina actually died twice before the game even starts. Bummer.
Despite being initially depicted as the antagonist, it's funny that Adler didn't actually do anything wrong. In fact he's 100% in the right if you fail to get the Promise ending.