Your sister appears to have anasognosia (lack of insight into her disease). It’s possible she may never gain insight into her disease. It’s far more important she gets and continues treatment than gaining insight into her disease, so forcing this agenda may be counterproductive. Her brain likely doesn’t function properly, and she may no longer be capable of understanding the nature of her illness. Insight can improve over time, it did in my case, but I would view this as a secondary desire or ‘stretch goal’ rather than a necessity.
It may be difficult to understand or accept, but understanding or insight into an illness isn’t necessary to treat a disease or live a better life. A person with diabetes or epilepsy or dementia doesn’t necessarily need to fully understand all aspects of their illness as long as they follow treatment regimes.
I had psychotherapy for a year and vowed not to take medication after expressing reluctance to medication to a psychiatrist who proceeded to attempt to prescribe five separate medications. I walked out of the office and never returned again. I was never handed a diagnosis by my psychologist or this psychiatrist and I think it would have been counterproductive until I was ready to accept it. Somewhere along the line, I declared I had schizophrenia to my psychologist and she calmly asked what that meant to me, she never actually said I was ‘right’. Labels are only helpful to the sufferer if they are willing to accept them, otherwise they are often a barrier to progress. It’s far more important to have trust in caregivers and doctors than any underlying understanding— this disease isn’t particularly well understood by experts either other than certain drugs seem to help. Insight can be helpful later on in recovery, but in the beginning— not so much in my opinion.
The following video should help explain anasognosia and methods to work around it. The speaker, Dr. Amador, wrote a book describing the LEAP method he used to help his brother with medication compliance called “I’m not sick, I don’t need help”. It’s often recommended to caregivers in your situation.
Disclaimer: While I am a part-time caregiver of my brother and father with SMI, I was diagnosed with SZA over thirty years ago. I’m an advocate of appropriate drug treatments for SMI, but I feel they are incomplete treatments and additional CBT, supportive talk and psychosocial therapies are helpful where feasible. Any drug advice is from personal experience or research and not a substitute for qualified Psychiatric care.