She could very well see herself as Ronald Reagan in that the third time's the charm.
But Reagan's first two times involved him not winning the nomination. If you fail to win the nomination, then you can keep trying again. But if you win the nomination and blow it in the general election, that's seen as a bigger failure. Because the party gave you your chance and you blew it.
What makes you think that though? Gore, Kerry, Romney, etc. All of them seemed pretty desperate to be president to me. I'm not sure what sets Hillary Clinton apart, that makes you think she wants the presidency more than they do.
She is already below 20% in the primary polls we've had so far:
https://uselectionatlas.org/FORUM/index.php?topic=258636.0https://uselectionatlas.org/FORUM/index.php?topic=261065.0I don't think it's obvious that she'd get more than 25% in the primaries, nor is that necessarily enough to win. Nor is it clear that she'd be favored in the general election, were she to win the nomination. Al Gore looked to be in better shape for winning re-nomination as of 2002, yet he opted not to try again, so not sure why we should assume that Clinton will want to try again.