>>536548842
NTA but I remember; here's the part where she says it.
What makes it hilarious is that she says it offhandedly and in a slightly dejected way immediately after giving her Mother her declaration of eternal love-through-murder and explaining why she travels around to kill Fatlice in every world they meet; it almost sounds like she's a kid who just found out they weren't getting to go to Disneyland the way she says it.

>>536548318
Ilias is genuinely annoyed with her at the hypocrisy and the danger posed by Hiruko, but >>536549243 is correct in that the real reason Ilias snapped wasn't for any 'moral' reason, but because Ilias felt like Alice I refusing to explain or confide in her anything and instead shutting herself off from the world was akin to a personal betrayal and being abandoned by her sibling.
It's understandable, but her reasons are much more personal than anything else.