Her main chance is if she becomes President before the election
From the point that Biden announced that Harris was to be his VP nominee the former Senator from California has been strong in the betting for the WH2024 nomination. In my view punters are over-stating her chances.
She can become President in two ways: First: if for whatever reason Biden is unable to complete his first term. In that situation she would go into the WH2024 nomination process as the incumbent and clearly the very strong favourite.
Secondly Biden could complete his first term and announce well ahead of time that he is not going to stand again. In that case there would be a normal nomination process with Harris having a strongish case as VP but having to compete against other hopefuls. Here being VP might not be so big an advantage except she probably has higher name recognition.
What we do know from the WH2020 nomination race is that Harrris hardly sparkles as a campaigner and, indeed, she quit the race well before the first primary. She avoided any electoral test. She would likely be up against the current Transportation Secretary, Pete Buttigieg, who won the 2020 Iowa caucuses. This became less of an advantage because cock-ups in the count meant that the result was delayed by a few day thus depriving the winner of valuable momentum.
Another problem for Harris running as VP is the huge security cost that her campaign would have to bear. These are one of the things that prevented then VP Biden from running against Hillary Clinton at WH2024.