Birth Mother Doesn't Know Who Birth Father Is

I found my birth mother several months ago but have not met her yet. She told me that my birth father is between two men and she says she only remembers their first names. She has a picture of one of the men. I also learned I have a half sister that was born a few years after me and also given up for adoption. My birth mother seems very sweet and I know she had a lot of pain from the adoptions. However, I cant help but feel angry that she doesnҒt have any information to provide me on my possible birth fathers. How could she not write down their names? Not let them know they may be a father? Not keep any information on them. Or, does she have more information but just wont tell me? IҒll probably never know. The more I learned about the circumstances surrounding my adoption and her pregnancy (it was kept a secret because her family was ashamed, the more pain I feel knowing that this decision wasnt made in my best interest. They were very religious so abortion wasnҒt an option. But I was a shameful secret that was kept and quickly gotten rid of. I feel that if she genuinely cared about my interest at all, she would have kept some information on the two men (they were not one night stands, but two men she briefly dated). It is hard to believe she doesnt remember their last names and didnҒt bother to write them down. Im struggling with this and donҒt really have any desire to meet her, I think a large reason is because of this. Knowing I will have no opportunity to find my birth father hurts, knowing that he doesnt even know I exist hurts even more. Has anyone had anything like this happen? Or relate? I don't want to continue being upset with her, any maybe with time it will get better, but I can't help but feel hurt by all of this.