I think it's been clear for a while now that Jimmy is going to lead to Kim's downfall. Ever since he returned, he's been slowly dragging her down, either directly or indirectly. So far, she's been able to weather the storm fairly well due to her tenacity but the pressure is starting to get to her. She's having to keep the firm afloat single-handedly while worrying about Jimmy's career and how long this will last, meanwhile the guilt of how she got Mesa Verde and what they did to Chuck is eating away at her. I'm not sure if she took on more work because she's worried about covering Jimmy's share of the firm or if she's just throwing herself into more work to avoid dealing with this stuff.
The question is just whether Kim wakes up to what's going on and runs while she still can, Jimmy realizes what he's doing to her and pushes her away, or if neither realize until it's too late.
