Or...random thought here...perhaps while she was in the middle of the crisis, it was easier for her to know what to stand for, morally.
But when she got into power...well, the power corrupted. And she died the moral death of a thousand tiny compromises that finally snowballed into the ultimate compromise.
The first time we met her, she blew up a school and tried to assassinate a political rival. That's not a 'tiny compromise'. In any case, from my vague memories of the series, it did not provide a reason why Winn would have become the person we met, and her characterization in the present sequences differed little from the biographical glimpses into her past. (That Kira should come to a grudging respect of Winn as a person, rather than as Kai, was particularly sickening, since Winn is exactly the opposite of Kira, a person who feigns faith for selfish advancement). I much preferred her characterization in the Terok Nor books, which showed her calculating nature.
Fictitiously yours, Trent Roman