Also just got the Revaire peaceful resolution with romancing Gisette (was romancing Clarmont unlike he dumped me :/ ). I had high Gisette respect and low rivalry/romance/friendship. I'd uncovered all the rebel secrets and I think you also might need high enough respect/friendship from Sayra (which is made easier if you ace the trial).
Yeah, this is something I'm not sure about either. I've never gotten the bar to more than 50% before the conversation with Sayra about Revaire's future, and even that I've only managed on my playthroughs where Katiya's legacy is my announced goal, so it seems like I definitely need that bump. I don't know anything for sure, but maybe befriending Clarmont and having high approval with the servants helps? I know you don't have to invite Sayra to an event to get the peace outcome, because I haven't done that before. It might help, though?
Yeah, being nice to servants definitely helps. If you get the gifts from Mrs. White and Sayra and Ria, then that's a sign that you're on the right path. I didn't invite Sayra out either, so that's not required (though inviting her to the Onvu tournament certainly wouldn't hurt). I raised the rebels approval by like 1/4 of the bar in week six and part of that was pulling off a successful ball. The other big boost was my convo with Sayra, which happened automatically. Couldn't say why she opened up to me and not you :(
I think it's just saving Penelope and the Summit (following Katya's , yeah. I bet that the servant scene before Clarmont's week 1 date also influences it. I was romancing Clarmont on this play through, so maybe that gave me more opportunities too? Antagonizing Gisette during the opening scenes helps too, but I think that may be more counterproductive if you want her to agree to peace...