After kim learned that jimmy had doctored chuck's papers kim had a short time where she had her own doubts about jimmy. Maybe thinking jimmy will try doing the same thing to her. In one episode kim goes back to double check her own mesa verde papers and I think it was because she had trust issues with jimmy. Maybe she thought jimmy might try to get mesa verde. Or maybe kim just went to double check just in case jimmy had forgot something.

Similar thing happened when jimmy gave his speech with chuck's letter in his hand. Kim just doesn't trust jimmy completely anymore. She can not know when jimmy is being real or faking it. Sooner or later kim will start to think if she is just a pawn in jimmy's game and whether their relationship is real. And it is just a matter of time before kim gets hit by jimmy's games.

I originally thought jimmy's and kim's relationship might end because kim grows out of their little tricks and figures out jimmy has bad effect on her. She can't continue with that because she has so much to lose and with jimmy she is just taking steps towards becoming more and more immoral and doing more and more illegal things. But that idea does not work because kim is more than just willing to go along with jimmy's plans at times.

What I think is that something happens that causes lots of problems of kim. Jimmy does something that falls on kim. Something that breaks the trust. Kim just can not trust jimmy anymore. Because jimmy is always willing to go much much much deeper into the illegal side than kim. I don't think jimmy does anything intentionally to hurt kim. If jimmy can take the hit for kim he will take the hit. But something just snowballs out of control and jimmy can't fix it. And kim has a lot more to lose than jimmy