This is honestly a complicated question to me. There’s a lot of history between Samael and Carmilla, plus Carmilla and her kids. The losses she’s gone through and the desires she has to keep her family safe means she’s had to give up a lot, she’s had to sacrifice, but she’s also watched sacrifice.
For Samael the easiest way I can think to explain her feelings and thoughts for him, they are endgame. Deep down, Carmilla knows that no matter what she and Samael were meant to be. That he is the only person who has seen her sins and understood her, wanted a family like her, and just they have this connection that very few people have and she wouldn’t call it soul mates because she doesn’t believe in that. But she does believe in always and forever, and that’s what she and Samael are.
Even with the distance they are always and forever, everlasting even when separated. She just can’t admit that because it’s terrifying and he’s been gone, she’s lost him once and even knowing he’ll always be here’s to actually take that step and move past their sacrifices is hard because she’s human.
She’s wasn’t immortal, something which Samael always has been, which leads to a disconnect in their view on history, years, and life.