She would have to resign as vice-president, to create that vacancy in the vice-presidency.
Then you wonder, what inducement would there be, for her to resign and spend more time with the family?
The Dems know their base will never stand for it if they simply dump her from the ticket. They have to find a way for Kamala to step down, and make it seem voluntary. They might create a new cabinet post for her to fill (Secretary of the Passage of Time?) and hype it as just important as her role as Vice President. The Dems then get her off the ticket in a way that allows Kamala to save face, and they pay her a boatload of money under the table in return for her accepting the new post.