I already wrote about this in my journal, but I am going to try to be a bit more articulate.
So, Ashe does not like dead people in camp. She used to be put off by people coming back to life in camp! See, Ashe would throw in her two cents, but she wouldn't push it. But it has swelled into an irrational hatred now. She cannot stand the thought!
Ironically, Ashe does not begrudge people who have come back to life. It wasn't their choice, and if they chose to. . . Well, people die suddenly, at times! Not everyone has the good fortune to die at peace with their life. So, she can understand that people might want to try to reach that particular ending. The fact is that, even if it's not fair, they have died. They cannot and should not have any bearing on the world of the living. It's not where they belong anymore.
Ashe had to painfully learn this in canon. She was manipulated by her desire for those she lost to return to her and to guide her. In the end, she comes to accept that while it wasn't fair that they died when they did, they are dead. Ashe can't do anything about that, but press forward. Really, while she does mention Rasler and Raminas in camp, she accepts they are part of her past. The future is what she's really looking at.
However, there's a keen difference between a god-race posing as your dead husband. . . And Rasler returning to life, truly. Ashe doesn't trust herself with that chance! Since her arrival in camp, Ashe has been hoping desperately that Rasler will never show. She is lonely, and she misses him. So, she isn't insensitive to the people who let themselves be carried away by a loved one coming back to life. She understands that expecting people not to involve themselves with those who were dead is expecting a lot. But Ashe demands it of herself, so she will hold others to that standard.
Then, Gabranth came! Which promptly made the above situation about a thousand times more likely to Ashe! It also started the slide from dislike to irrationality when it came to those who were dead. This is someone that Ashe knew from before camp that died and is trying to regain his life to her. He insists on acting as Larsa's guard and speaking with her. Now, Ashe has some residual anger for his killing her father, but it's set aside for the most part. She accepts that her father is dead, whatever the circumstances were. She is as civil as she thinks should be expected of her even. Ashe left the cabin, refusing to sleep under the same roof as him, rather than demanding that he leave. (Ashe has never put this on air, because a queen does not leave. She makes the other person leave.) She also lets him continue to be around Larsa, despite her aforementioned thoughts on the topic. But Ashe is no less angry at this course of events.
On top of that, she caught a glimpse of the happy Maes family. This is most likely the straw that broke the tsunprincess' back. Before everything, Ashe was happy. She had a husband that she loved even if they were arranged to marry one another. Even now, Ashe understands that she probably will not have a loving husband and a happy family. Lighting does not strike the same place twice. But that doesn't stop her from wanting it. So, it hurts somewhere deep to see others so happy with something that she can't have.
At this point, Ashe is staunchly refusing to speak with anyone previously dead and involved with them. She doesn't want to lose her composure over something that everyone else does enjoy. Ashe knows it isn't her place to rain on everyone else's parade, but her tolerance level is really low. So, if she snaps a little? She's allowed that much in her mind. Then, Zidane dropped something of a bomb by saying Gabranth was not only alive in camp. . . But in some other strange world! So, Ashe has something of a vendetta against this, because she will tolerate all of this until it even comes close to involving Ivalice.
Then? Then, Ashe starts swording people in the kidneys. -Pheeew, I can't believe I managed to write all that. \o/