I don't know enough about the process.
What I do know is:
Yer average Frenchman has been hurt by austerity, his job-for-life is gone, financial uncertainty is the new normal. Throw in Charlie Hebdo, Thalys train, Bataclan, Saint Quentin, Magnaville,Promenade des Anglais, a priest slaughtered at his altar, various shit in Belgium etc...
This average Frenchman is being offered: Same old, same old by people who have been happily lining their own pockets for years and continuing integration with the rest of the EU, or a racist who is offering job security, a return to financial comfort and a solution to these endless terror attacks. She may well be a racist, she may well not be able to deliver. But yet again the options are more of the same vs. something else and the something else is what people are after.
So yeah, maybe 1st round, 2nd round, won't get enough support even if she becomes president, I really don't know the figures. All I see is how shit the status quo is only one person in the running that is offering anything but the status quo.