She closes her eyes, and she pictures a life with Lee.
She thinks she knows what that life will look like, knows the different Kara she will have to be if she ties herself to Lee Adama, body and soul (never mind that they've been tied together since the day they met, never mind that he's always first in her heart and mind, never mind that she can't bury these feelings, no matter how often and how hard she tries), and she thinks, I will ruin us both.
So the next morning, after she finds Sam (who loves her because, not in spite of) and he laughs as he pulls her into his arms, she asks him to marry her.
BSG Kara/Lee, it's braver sometimes just to run
She thinks she knows what that life will look like, knows the different Kara she will have to be if she ties herself to Lee Adama, body and soul (never mind that they've been tied together since the day they met, never mind that he's always first in her heart and mind, never mind that she can't bury these feelings, no matter how often and how hard she tries), and she thinks, I will ruin us both.
So the next morning, after she finds Sam (who loves her because, not in spite of) and he laughs as he pulls her into his arms, she asks him to marry her.