A this point, it's not even about the brothers. I just want to see Aunt Umbridge get some satisfying comeuppance.
The sad thing is, you really, really can't blame Hari for her little funk here. Her brothers, especially Erich, have given her no reason to think that they'd even care if she died. And as kinda abusive as they were, her brothers filled a hole in her heart where a loving family should be, so she stuck with it to the point of developing a different complex.
It really is most frustrating with Erich. Because while he's just being an immature kid with a perfectly reasonable response, it's also such a bratty response that's almost single-handedly making this situation go from bad to unmanageable.
Edit: Okay, wow. A lot of people are more hung up on her mental age than I expected. It really isn't that complicated. If anything, this chapter drives in why she's like this more than ever before.
The bottom line is that she honestly can't communicate with her brothers, because they've mostly done nothing but given her shit and her most predominant memory with them is probably still them repeatedly telling her that they don't accept her, she's not their sister, and that she doesn't belong in their family. And we're talking two childhood's worth of that.
Stop expecting her to be some brilliant scheming noblewoman in a child's body, because it's been made abundantly clear that the first time around, she didn't have a chance to properly mature or even communicate with anyone. The main difference from her going back in time is a greater self-awareness and it's evening the playing field, not giving her an advantage.