James - The most important facet of this is that you know someone is suicidal. When someone is suicidal - you MUST get them to help. I don't care if you have to trick her to do it. I read red flags of considerable warning in your letter. She needs more help than you can give her. I've been where she's at, and I do not think for a second that she will not kill herself.
She needs to be in a place where she is safe enough to open the floodgates that are drowning her within. She is severely depressed and I'm glad she has you. You may be the only anchor she has to staying 'here'. Before she can deal with rape issues and self esteem issues, she needs to want to live. And yes, I'm completely suggesting that she go into the emergency at the hospital to talk with the nurses and doctors and very possibly - ideally - admittance to a psych ward.
I had to put myself in the hospital. Actually, others took me, but I shook my head 'yes'. I spent three months in there. I 'had' to live because I had two young girls at home - the anchor to life 'here'. While I didn't have friends or family I could really turn to, I couldn't leave my girls motherless. And that was at a primal level because I had stopped talking - and was suicidal.
Your cousin doesn't seem to have an 'anchor'. She's not going to want to get help, and she's not going to like going to the hospital - but when it comes down to it James, you keep reminding her that you will remain by her through it all and if you have to - call the cops.
If she really is determined to take her life - no one can stop her. However I truly believe from what you wrote that she is not unreachable. Instead of reading books - start calling hospitals and police to see what can be done. You are talking about a life here. If she says you lied to her about your word - you say no, i did not - I care about you and I'm going to see you through this. These people will help you, and I'll be there for you.
James - you seem to be a very caring man and her life right now - is in your hands. If you try to get her help and she kills herself - you did everything you could.
She's suicidal and severely depressed. Call the hospitals James. Please.