Hello, my sister has not improved for 3 years now! She has been in many hospitals, seen many doctors, and has been on many types of prescriptions but her mental state has remained the same. Please give me any advice!

Here is her story:

Since she was 3 she had a passion for piano. She loved playing and composing and was determined to make that her life-long goal. She has always been different. Her kindergarten teacher told my mom that she was going to be hard to raise (which was an understatement). She never fit in with anyone until high school where she had a small group of friends that just tortured her. When she was about 16 she went on a trip with her friend to my father's friend’s house about 8 hours away for the week. Her and her friend went to a party there where she was slipped a date rape drug and she got raped. The guy tried to drown her afterwards. She ended up getting herpes from it and was close to committing suicide.
She went to college for piano and went to several different ones before going to one in a major city about 6 hours away. Her first apartment there was a small studio that was nice, but cost $1000/month. She says that this was the happiest time of her life, going to school and taking piano classes, then afterwards practicing for 12 hours a day. This is the first time in her life that she didn't 'copy' some one else. She never really had her own identity. She has always had one friend that she wanted to be and completely copied this person in every way. She eventually got a very good piano teacher that was very strict. After going to school for about a year here, her loans started to kick in and she was forced to get a full time job. Only being able to practice piano an hour a day, and take only a few classes, she was crushed. When her teacher told her that her playing was degrading, she got very depressed. Because of her obsessive personality, she thought about this constantly, and would always call home crying about it. She frantically tried to contact wealthy people telling them her situation hoping they would help her pay her bills, but this never happened. She had to move out of her loved apartment and into a small old one.
Here, she met a woman that was to become the next person she would copy. This woman told my sister that if she just accepted The Holy Spirit into her body, that all of her problems would go away. She told her that she would feel the spirit enter her after saying a special prayer, and that it would control her according to God's plans. Excited that this would solve her problems, and her inability to doubt anyone (her whole life), she got all worked up and said the prayer. She said she felt something enter her and began hearing voices. The woman began taking control of her and made her do very odd things. She made my sister cast out demons regularly, donate all of her clothes and get long baggy dresses, cut her hair very short, eat special food, and buy her anything she wanted because God wanted it that way... They then began doing the Chabot (a Jewish ceremony) every Friday (again because God said to). One time while doing this ceremony, she said she felt something enter her that she thought was God. Eventually the voices started saying that they tricked her and that is was actually the devil, or a demon, that she accepted into her. She stopped sleeping and began going crazy thinking that these voices she is hearing may not be God. This whole time she kept her family in the dark about everything, only telling us that she goes to church once a week. One day she called home telling my mother to look out of the window because God is coming. Scared and confused, me and my mother flew to her apartment the next morning. When she saw us she just said hi, instead of being surprised. We kept asking her questions until she snapped and poured water on our heads with a huge grin on her face saying that she is blessing us. We called the cops and she was taken to a hospital for multiple physical examinations (looking for drugs, tumors, and other possible causes). They gave her something to make her sleep and seemed to snap out of it when she woke up the next day. She was set up with a psychiatrist and therapist and began taking medication. Missing work and school, my mother and I had to go back home. We didn't know it but her condition was getting worse and she was admitted to several psychiatric centers before coming home for Easter. A couple of minutes after entering the door she had a panic attack and we brought her to the hospital. From here she was admitted to a private psychiatric center.
Usually she would get dismissed after a couple of days because she is very good at pretending she is fine, but this time my mother and I told the doctors that she is just faking it. Until now she has only been on a low dosage of her medicine. She was told that if she didn't up her dosage that she was going to be forced to, so she agreed to. She finally filled us in about everything that happened where she was living (voices, demon attacks, seeing Jesus, getting thrown against her wall by spirits, knowing that she is going to die any day, not being able to hear herself think, completely numb body...). After a month in this hospital with no improvement, she was admitted to our city's psychiatric center (which was a legal battle). She was given anti-depressants and her mood seemed to get better. The doctor assured that when the depression goes away, so will her delusions, but they didn't. She still 'knew' she was soon to die, felt demons enter her all the time, could not hear herself think, and still had a numb body.
After being there for 6 months (about 5 months ago), she was able to come home. She ended up publishing a CD of all her piano songs that she has composed, but has now sold her piano (that she has had for 10 years), and her keyboard and says she will never play again until she goes to heaven. She is still exactly the same: demons enter her, she can't think, can't feel, and thinks she is going to die soon. She has tried about 8 different medications. She now refuses to see her therapist because “she can't help”. And right now, as I type this, she is at a church that picked her up and she is probably getting prayed over (we don't know where, or when she is coming back, and have no way to get a hold of her, she just left saying she is going to a church).
There are good and bad days (mostly bad). She smiles and jokes every once in a while, but 99% of the time she is on the internet (while we are at work) probably looking up religious things. She keeps saying that she is going to move out because we don't believe her (that she is getting attacked by demons), and because we are sinners. She cries because we will not repent and accept The Holy Spirit like she did, because she doesn't want us to go to hell.
She thinks that all of this stuff is happening because she did the Chabot. The woman that got her into all of this has stopped talking to her because she is not giving her money anymore, and my sister is crushed by this. She says that if she called tomorrow and told my sister to come back to her, she would jump on the first bus.
I have no idea what to do. She constantly fights with my mother because my mother fornicates with her boyfriend. She refuses to see the therapist, or change her medication. I think one day she will disappear and we will never see her again (maybe tonight).
PLEASE give me any advice that you can. Even though this is a long post, there are a ton of things that I have left out, so if you have any questions, please ask. Thank you!