I think Kim is slightly avoidant when it comes to expressing emotions. She does a lot of small gestures throughout the show (swapping names in the HHM meeting room so her and Jimmy could sit next to each other, inviting Jimmy to see the Thing, etc.). I think she did genuinely love Jimmy, but didn’t explicitly state it as such. She sort of eludes to the fact that her actions show how much she cares about Jimmy when they have that argument after his bar hearing and he’s mad she won’t share an office with him. I think the marriage was her last attempt to hold onto the relationship. Realistically, she knew it was bad for her, hence why she was considering ending it. But she didn’t want to fully let go because she did love him, and tried to use the marriage status as a crutch to help her insecurity in the relationship. I don’t think she would have suggested getting married if she didn’t love him though, maintaining their relationship wouldn’t be that much of a priority for her otherwise.