Kim and Jimmy are good friends for sure since they are always looking out for each other and being happy/sad for each other, but are they, or were at one time, romantically involved too ? In the episode RICO, when Jimmy tells Kim that he has passed the bar exam, she hugs him excitedly and kisses him on the lips. Nothing else is clear afterwards. Whether they had a relationship at some point or currently have feelings for each other is ambiguous. Are there any subtle hints in the show ? What is the nature of relationship between Jimmy and Kim?
I strongly suspect they've had a sexual relationship at some point. Brief fling, something more, difficult to speculate.
In one episode, we see them sharing a cigarette. While not always an indication of intimacy, I've never known anyone in my life that does that without it meaning something.
In another episode, Jimmy calls late at night, and she says something snarky about he better not be calling for phone sex, but the tone of her voice indicates that the idea doesn't repulse her, it's merely unwelcome at the moment.