Looking it up and examining the motives and context (as someone who didn't know much about it beforehand)- my opinion is that Corday is a perfect example of the "bleeding heart moderate" who has infinite sympathy for capitalists and even in some degree the nobility, while sparing little in comparison to those victimized most by society, and with no true loyalty to the revolution and the dignity and self-determination of the masses- a natural backstabber, striking when and where the revolution (or specific revolutionaries, in a very literal sense in the case of Marat's assassination) was most vulnerable.
In another life, perhaps she would have been a Gorbachev, or a Yeltsin. She strikes me as exactly the kind of person who any revolution must defend itself against, a threat just as dangerous if not more so than any external enemy.