I think this is one of the main ways that I am different to my family. I have often thought that the ability to self examine is so fundamental to change and to managing life in general. Some people don't seem to have the capacity for it.They think other people are the problem.
I have an aunt that is extremely unstable. She can't eat if others are around her and fears choking so holes up at home on her own, she has drastic fallouts with everyone around her, has OCD, struggles to travel anywhere because of severe anxiety. She literally shakes when in social groups and randomly looses her temper. She keeps going from being well off to bankrupt as she has spending sessions that wipe her out. But according to her she is totally fine. People and the world are just problematic and to blame in every possible way. She will say this whilst barely being able to stand with all the shaking. It's sad.
I am sorry that this something you had to deal jmni. I have been watching documentaries on hoarding recently and have thought how truly awful it is for the family. It must literally be crushing. The level of denial is also usually astounding and clearly demonstrates how powerful denial and self delusion can be.She is a hoarder.
What you describe is interesting. You are saying she is very unstable and has many mental health issues and yet a sexual assault left her untouched and she shows no signs of being affected by it. I wonder if she has had other trauma in her life. Sometimes I think her type of issues are very often linked to general abuse and bad parenting but without a lot of trauma. I find it very interesting how different people react in different ways. Human beings are endlessly complex and unique.