I used the "Bring Peace to Revaire" guide and it worked on an Ethical Widow, see link below.
(https://docs.google.com/document/d/17P7Q0qq6xIPYoGJYAAzh1RH6SLvRHKFvjd7jSAfGxXU/...)
Interestingly enough, I just did a second run-through (Jiyel) while following it more loosely, and I managed to get Revaire's good peace ending after forgetting to invite Sayra to Onvu tournament, so I don't think it's as necessary as boosting her friendship. Also, I chose the Katyia's legacy ambition for both characters, although my widow was lying and moreso interested in alliances.