It’s true Rose was treated terribly and somehow the expanded materials by other creators do far more justice to her than Johnson did his own character. I’ve written several posts about the discrepancy between Cobalt Squadron, the junior novel starring Rose, and TLJ/its novelization.
It’s not even the fact that she committed a shitty act of violence against an unthreatening ally that bothers me, either. People can do awful things and then make amends, and those are some of my favorite kinds of stories (e.g. Zuko from ATLA). What bothers me is rather the refusal to admit, both on the part of the narrative and the fandom, that what she did was shitty and wrong. Not only does it result in the terrible and racist implication that Finn deserved violence when he wasn’t threatening Rose in any way, but it also takes away from Rose’s own story of learning to cope with grief without hurting others.