I don't recall reading who, if anyone pulled CA off of KC either. Perhaps KC broke the hold or CA realized what she was doing?
I am not sure it was a fmaily member that told LP. My guess is that RG told LP. In the last doc dump, RG relates that LA told him, IIRC, during a phone call. RG has communicated quite a bit with LP, so that's my uneducated guess. (Note, I do think that the fights the neighbour reported hearing between CA and KC might be related, especially as one seems to have been on the 15th of June.)
I should add that I am on the fence on this one. I do believe that CA & KC had a very large blow-out, but if KC is the sole source that told Lee, then I am not certain that it wasn't another lie exagerrating the fight to make CA look bad to Lee. Not sure - waiting for something concrete to sway me.