Rose didn't "retcon" her insecurity away, the drinking was just an unfortunate side effect. She got over herself when she talked with Roxy and realized they both related to each other over drinking to their dead mums and don't need to compare and feel burdened by their parents anymore. That put a close on the sub Arc for her character and didn't need to be addressed anymore, because it served it's purpose.>This isn't life, it's a piece of fiction.>"We don't have character arcs Rose"
Not everything needs a hundred hours of introspection to wrap up, especially for stylized fictional characters. They're not, you know that right? Your entire notion of a symbolic character arc, coded through a cookie cutter narrative is inseparable from your notion that a naive vein of storytelling is the only way to go about things.
The characters are an end to themselves.
Not a means to something higher or another end, or an 'Arc' or whatever. Just them. This is like, Rose's entire pseudo-arc realizing this.
Basically what the hell do you want, Rose to go through a hundred pages of therapy session over her drinking and dead mother?