Shes definitely exploring it, book tour and other actions show shes trying to stay in spotlight to leave her options open. Several current and former advisers have hinted she might. More likely than numerous other candidates listed in this market 

There are numerous feasible potential candidates that are missing from these 2020 presidential contracts:

Hillary Clinton

Michael Avenatti

Michelle Obama

Michael Bloomberg

Beto O'Rourke

Each of these has at least a 10% chance of running, and each has at least a 5% chance of winning the nomination if they run.