One instance of choosing the right thing, especially in the wake of having enabled the empowering of the Pai-Wraiths and Dukat, doesn't make a redemption. But I think it would have been enough for many of the major players involved to say that she deserved an opportunity to attempt atonement.
Honestly, I legitimately think that Kira would have said that, provided Winn step down from Kai (something that, had she survived, I think would have been a given - you don't open the door for the devil and still get to be the Pope), that allowing her to seek the forgiveness of the Prophets would be the right thing to do.
But I also feel like the thing that Winn would have done in the aftermath would be to retreat into seclusion in a distant monastery, considering that, even acknowledging her ego and jealousy as motivation, she would be in a position where she could not serve as Kai, and would definitely have had Vedeks and the public as a whole demanding she step down. And, yeah, she does end up feeding on having that proverbial spotlight, so I don't think it would have lasted forever - we saw in her earliest appearances how willing she was to let others act in her name, both in the assassination attempt on Bareil and in her association with Jaro and the Circle, she could easily have found her way into some other movement where she could work in the shadows and claim it was for the good of Bajor.
Still, it is an interesting possibility to consider. Again, I don't think it was quite "redemption equals death," as the trope is called, but I do think that Sisko and Kira in particular would probably have said that she deserved the opportunity to attempt to atone.