They're similar in this, like they are in most things. She watched her sisters fall, and he his Order. Of course he understands—and that's a comforting thought, even if she wishes it didn't have to be. So is thinking that her survival, as unlikely as it was, is some sort of... defiance to whoever struck her sisters down. They didn't fully succeed, and that is, indeed, something.

Not yet, anyway. Like she told him in the tomb, nothing will bring her people back. Even without the holocron, Cal might be able to find other Force-sensitives, or maybe even other surviving Jedi, but Merrin has no hope that any of her sisters survived. She's the last one. From here on out, only time will destroy the Nightsisters of Dathomir.

But Cal is trying to cheer her up, and that's also something. She smiles slightly, even if it's weak and fleeting. "Yes, that is something. We still survive."