It actually seems to me that her brother; not only was he abused as well but he in turn sort of also made things worse for her childhood. I can't quite pinpoint it but I read some panels that gave off major red flags, I'm anticipating more lore drop about them so that I can make my final judgement since I don't really see why it's unhealthy (yet) for her to cut off a family member that made her life worse regardless of whether or not he was abused.
I understand she has every right to cut the brother off but let's not forget that they both faced abuse they just react to it differently her memory loss most likely has a lot to do with that dream her brother had of her covered in blood i don't think he made it worse for her but she shut it off because of the pain and the separation between her and her brother musta been the breaking point losing someone that you felt was a comrad in the struggle with you is painful I wouldn't assume he made it worse she doesn't even remember that she's just saying she has no memory of him I'm her childhood meaning she's like I said BLOCKED it all off it was painful for her to deal with as a child and like she said with no memory you can't feel anything for a person his practically a stranger to her cutting him off as "family" is better for her because like she said she doesn't have any fond memories of family.
Bruh that's not fuvking healthy go get your brother bruh