Can I have my mentally ill sister declared incompetent and if so, how?

My sister is a 47 year old diagnosed with bi-polar disorder. I believe she needs another diagnosis of schizophrenia, however she does not see a doctor on any kind of regular basis. She is homeless. She is a sex addict. She has 3 children, none of whom she has custody of, but sees the 2 teenage children regularly. The 4 year old was taken from her and adopted out of foster care. She did not know who the father was or half of the names of the men she slept with. She has been going down a path of self destruction with a man that has lured her into his world of sex addicts. He manipulates her with a powerful psychological lure (for her, anyway) as he lives on the street we grew up on. My other sister lives in the house we grew up in. She has destroyed it as she is a hoarder and has too many cats that deficate all over the mounds of "stuff". The house is a horrific mess and could be on that TV show easily. I could add so much more detail. It is a nightmare.