The only difference is difference between them is that Diane is slightly younger and is just now hitting her shit stride, has fewer people she's important to, and isn't the main character. She already sent Bojack into a spiral that lead to his break up with Wanda, and she has hurt PB time and again, and the inevitable divorce is going to go real rough for him. Considering those are the only two characters she has had any real interaction with, she's not doing so shabby in the "fuck things up for everyone close to you" department.
They're both intelligent and sensitive people from shit families that escaped to LA to follow a sub-culture's false promise of happiness, only to find the promise was empty and leaving them empty handef without any direction on where to go next. With Bojack finally getting his shit together, I think we're going to see a lot more of that parallel.