I think if "they" had that much control over their folks, Biden would have stepped aside already. The Pwers clearly wish him to, but he's gone all Angry Granpa and is holding on to the bitter end. I see no evidence they have any more control over Kamala.
She backed out of the primary in 2020 specifically to position herself as a DEI VP pic, and later run for President, a position she clearly wants. I don't think she'll settle for 9 months of seat filler. She wants the job.
Hell even if Joe makes it through the election and loses, I expect we'll see Mrs. Harris again in 2028 touting her experience.