Simply put, yes.  I think that it is critical to understand Flaubert's point in life when he writes "A Simple Heart."  One of his last works, Flaubert wrote it at a point where he experienced the deaths of his best friend, George Sand, and his mistress, Louise Colet, both impacting him on personal and artistic levels.  Flaubert began to recognize the truth of Sand's warning to him that Flaubert must strive to compose "literature of consolation rather than desolation.’’  For the author that wrote Madame Bovary, constructed a portrait of human misery and nothingness that haunted any reader who grasped it, these words proved to be cathartic.

In my mind, it is with this hope of constructing literature " of consolation" that Flaubert believes Felicite to represent a type of saint.  Flaubert is deliberate in constructing her as being so distinct from her world.  No one in her world resembles her in any way.  Felicite represents that "haven in a heartless world" that Flaubert never quite envisioned in his work up to this point.  It had to be a moment of reckoning for him, experiencing death and loss at such a close proximity, that if human beings had any chance of salvation, it resided with Felicite.  Her absorption of religious fervor is another contributing factor to how Flaubert could have seen her as a saint.  However, I think that it goes deeper than this.  Flaubert believes that Felicite is a saint because she does not take the form of the world around her.  In a world of increasing materialism, the rise of the bourgeois, and the construction of society into self- interest, Felicite is salvation.  She is a character of "consolation," whereas Emma Bovary would represent "desolation."  Towards the end of his life and with no doubt some sense of fear present, Flaubert was able to develop a character of salvation in Felicite, her love being the answer to what was wrong with the world.  It is in this light that he sees her as a saint, someone who is capable of rescuing humanity into "consolation" as opposed to plunging it into further "desolation."