It was obvious there would be some level of friction there just based on how Kamala tried to attack Joe on busing during the primary debates. She damn near had custom t shirts ready made before the debate was even over. It was a calculated stunt.
I was surprised Joe picked Kamala after that alone to some degree, though being the career politician that he is, he was comfortable making a demographic play for electoral purposes which made her useful. I dont really see what expertise she had that could help bolster him in terms of actual governance.
The question is whether or not there was a handshake deal for Kamala to be the running mate with Joe promising not to run for re-election, if it was undecided or if he said he was running for both terms.
I have the inclination to believe that Joe said it was unlikely but has since said he plans on running which has upset the Kamala camp. He also tasked her with working on the border similar to how Trump threw Pence to the wolves for covid. In Joe's defense, they probably figured it could give her a nice notch on her belt for her resume if it was to work out.
Its puzzling to me as to why Joe hasnt had her more front and center in dealing with legislative talks with the Senate she was just a part of. Yes, he campaigned on being a bipartisan deal maker but he has also been out of congress since 2008 and hiding Kamala from those talks give off the impression that she cannot get things done even though a majority of the senators were just her colleagues. It's just simply not a good working relationship.