How do I help angry b-mom?

I have posted here before and you all have been so helpful. I'm hoping you can help again. I have been in reunion with my bmom for 1 year and it has been up and down (mostly downs recently) and I had been trying to get her to tell me the birthfather's name for health reasons (genetically passed deteriorating condition which was also the reason I initially looked for her). She finally told me but with so very much anger. I don't know how to go on with her from here. She never told anyone about the pregancy (late 70's very small town, i.e. a couple hundred people) until 2 weeks before giving birth. Her oldest brother found out, he told her parents, they immediately made adoption plan in much secrecy. She has told me so very many stories about the circumstances and I finally got the original social worker's version this week. Every version is different but the basic gist from each is that it was a one night stand with a guy who worked for her father. They scheduled a c-section over spring break and she went back to school as if nothing had happened (her words). She never told her husband about me or her 3 kids (although I am still in amazement her husband never noticed a 1970's c-section scar when they had a baby together less than a year after she gave me up as well as the fact that she kept an 11-pound baby pregnancy a secret in that small of a town). She is very close with her children and ironically one of her teenage daughters just had a baby and also kept the pregnancy secret. Her husband however has a child that he gave up for adoption right before the two of them got together (i.e. golden opportunity to tell him about me!) and they are in reunion, however it is not a good situation (he asks for money, etc.) which is why I totally understood her taking a while to trust me. But I have done everything she asks and kept my identity and existence a secret. I've also never asked for anything but information. She says that she never dealt with what happened. I tried sending her to this site - big mistake. I thought she could read about other people that had gone through similar experiences - I know it has helped me. But she saw it as a personal attack, basically like she does anything else I say. She also finally told me the bfather's name but only after blasting me saying that all I ever do is test her and call her a liar (which by the way I never did) and that I am the bad person and that she may just send me over to her brothers who will "chew you up and spit you out because someone like you could never handle someone like them." What? Why? B/c I was born as their niece? Basically every conversation we have had since I first contacted her has involved me repeatedly apologizing for my existence and I honestly don't know how much more I can take of it. One minute she tells me she loves me; gives me cookbooks and pictures. The next she tells me all I ever was or will be is a stranger to her and I am a horrible person. Do I end this relationship? I've written several draft letters to her expressing my hurt and also that I hope she can come to peace and if so that I will keep my contact info updated. Can I help her deal with this or do I just let her be? Do I send a letter or just stop contact (it has been about 3 weeks since she sent me the last email)? Any advice would be greatly appreciated. Thank you.