Source: https://ballotpedia.org/Ballot_access_for_major_and_minor_party_candidates

Friendly heads up to all the conspiracy theorists here. Every state has ballot access laws which are requirements that have passed as much as five months ago. For instance, Alabama's ballot access law has a sign up date of Nov. 8. Other states were similar and went up to the end of February. Hillary and Michelle can't run at this point because they haven't signed up, paid any fees, or anything else. There also is an extremely low chance of the picture happening because of three reasons:

1. Hillary couldn't get the younger vote in 2016
2. A shit ton of people hate her for various reasons (Democrat, seen as elite, evil, etc.)
3. Psychologically, people see her as a loser because she ran a campaign and lost. Unlike 2008 where she just failed to get the nomination, in 2016 she went all the way to the end and lost.

There is zero chance Hillary would be picked as VP because it would not help Biden at all. Expect a Warren VP or perhaps Michelle, but not Hillary. So please stop with the theories that she will magically show up and try becoming the nominee. It's not possible. She doesn't have the support she did in 2016 to circumvent the law and do it regardless.