This will be long so I am sorry

I am 25 year old woman from India. In December 2005 I met this 33 year old woman online. She writes exquisite poetry and is intelligent and just a beautiful soul and I am a bisexual so to cut the long story short I fell for her. Initially she told me that she had been raped when she was 5 and later on she mentioned that she had been diagnosed with schizophrenia when she was 23 years old. The she also mentioned that her father had molested her. When I first told her that I loved her she said I wanted to use her for sex which was kind of 'not possible' since we live almost 800 kms apart. She even sent a mail to my friend that I was desperate for a lay. That hurt me but later on I learnt that it was part of her paranoia and all. Then we started writing letters to one another. And then she told me that she loved me. She painted me like some angel (all along I tried to remind her that I was only a mere mortal) I wanted to meet her and whenever I mentioned that again she would accuse me of wanting to use her. I even offered to fly to her city for one day and meet her in a public place or in the presence of her friend so that she could be rest assured that I wasnt using her but to no avail.
She claimed to have had a long history of men using her. She has not been taking medicines or seeking therapy. I tried to talk her into doing that but she would get really angry if I tried that. After 5 months or so of being a couple she asked me to marry her on the phone. I was confused. Here she wasn't allowing me to meet her and sending me text messages that she couldnt sleep with me ever and then she was asking me to marry her. I mean how could we get married without getting to know each other better. I told her I wanted us to take things one step at a time but then she felt I was rejecting her which once again meant she was right in thinking that I just wanted to use her. Oh and I have reason to believe that she was not always faithful to me in this time period. Then one day she says that its best for us to just remain friends and the next I know she tells people that I used her. By then I had read about schizophrenia and tried practicing being patient with her and remaining calm and passive but at times her accusations left me feeling absolutely heart broken. I mean here I was thinking about how I could be with her or helping her and I was being accused of wanting to harm her. The final straw was a few weeks back. Now she is in love with some 22 year old guy. And I dont know what to do? I feel I am about to lose my sanity cause I spent nights worrying about this woman and I dont even know if she ever did love me. DId she? Or was she confused and was I just a part of those delusions?
I know she is not to be blamed for her behaviour but now I feel like I should die or something. I mean I really love this person and if nothing else I want to protect her but I cant cause she just hurts me too much. And then she sends ecards to say she is sorry but nowadays it all seems so meaningless. I dont know what to do. I worry that this love interest might not turn out the way she wants it to and then it will be even worse. I know I should have been more understanding, particularly in the initial phases or then I should have tried to just be a friend but I fell so hard for her that I didnt think over her information of being a person with schizophrenia that carefully. I am a clinical psychologist's daughter so I would like to believe that I am sensitive enough about these issues but now i dont know if i can take it any longer. I feel so tired and so depressed all the time. I dont have any less issues of my own. I lost my only brother almost 3 years ago and I was a caregiver for him for an intensely traumatic period of 3 months. He died in front of my eyes and I am still not over it in many ways. I have never received any support from her about my brother. Now I dont expect it. Today I read her write some pretty bad stuff about me to a friend on a public community forum. I just want out but I am scared. I know she needs support and help but sometimes I wonder at what cost......my sanity? cause sometimes it really feels like i might lose my mind. is it ok if I back out? Emotionally and physically I am too drained. She isnt willing to take medication and I dont know what else I can do? And no matter how much I decide not to be affected by her accusations now I cant take them anymore. Maybe it is because of my brother's death that I have become so sensitive but I cant take it. And I cant forget her. She is my absolute love and I just am feeling so betrayed.
Also I cant shake off one thought....did she ever love me? or was I just a part of some delusion or hallucination?
Is it ok if I walk away? I am feeling so guilty. Does that make me a bad person? Please help me as to what I should do. thank you