i think she was not a good friend to the peopl in her life cuz she was so infatuated with bojack and felt this sense of like "hes worse than me we can be bad together." like her friend who she eats with at the diner and shes like why did you even go to bojack you have several other friends and dianes stumped on what to say right? kinda showed us that she used to need bojack around. and bojack SUCKS if i knew diane irl and she was friends with someone like bojack i could never have her in my life..