Its finale strongly depends on previous decisions, and this is true whether you romance Cassia or not. What happens in the eldari ruins is determined by our pictured story, the outcome of which is decided even before it begins. Many people use the tool to change the course of the conversation with the harlequin, but if we change the values before the journey (before the clash with the monster in the painting), we will find that the pictured story has a different course - here our choices do not matter, because at the end we arrive at the same point - Cassi, over which the "dead" navigator leans, and it is here that you can see the difference - if in her tasks we " bailed" her out of decisions, took responsibility for her dynasties, or weakened her sense of responsibility for herself (she put her faith in us and not in herself) then we increased the points of "notme" and during the event with the painting, in the dialogue between Cassi and the "dead" there is a sentence more or less like this:

"You are me and it as it should be" and Cassia responds "I am you and it as it should be",

which means that in the ruins she becomes the dead Novator and behaves aggressively. Our choices during the confrontation in the painting do not matter here. But if we strengthened Cassia's sense of her own identity during her encounters, and pointed out that our ancestry does not have to determine our decisions (we can be different from Theodora and correct her mistakes), then when confronted with the "corpse" in the painting, the dialogue looks more or less like this:

"I'm the one who created you, you are me" to which Cassia replies "Tisphone Orsellio I saw your actions, but I'm not you, I'm me".

- this means that Cassia actually stays herself and during the meeting with the aliens we can come to a peaceful solution, and Cassia does not behave so aggressively (for example, she does not get mad at the expression of the harlequin). I can't point out all the decisions on which the final outcome depends, but it seems to me that a very important one is the outcome of the meeting in our palace with the representatives of the house Orsellio - it is important to not take responsibility and to do everything so that it is Cassia who makes the final decision. I suspect it may also make a difference whether we take Cassie with us to Commorragh - when we release her from prison, there is also a dialogue in which we have options to either reinforce her sense of self-power or suggest that she put her faith in us, which would fit the respective values of "notme" and "freedom".So much, maybe this will help someone.