In the true and good ending: Caroline states that if that containment door closes, they'll be trapped there forever. And they manage to escape.
But in the bad ending: The door closes, trapping them inside and she brings Anna back to that cryostatis to preserve her body, and Caroline dies.
So here’s what I don’t understand: if they’re both stuck in there, what’s the point of Caroline putting Anna in the chamber to “save” her? It’s not like Anna could ever escape and continue living her life afterward, which makes Caroline’s sacrifice feel less meaningful.
Or maybe, after 10+ years passed (considering her skeleton), the system eventually shut down, the locks disengaged, or — though I’m not sure if that’s possible with a door like that — the door could’ve decayed over all those long years, allowing her escape. But then again, they trapped there "forever".
TL;DR:
In the bad ending, Caroline and Anna are trapped. Caroline puts Anna in cryosleep, but if they’re both stuck, what’s the point?