Just found out that I have a half-sister out there somewhere........

I'm looking for articles or a support system on the topic of finding out that you have a half-sister. I am 39 years old and my mom just told me that she had given a baby girl up for adoption back in 1965. It was a closed adoption and since so many years had passed, she thought that she would have already pursued looking for her birth mother. Mom found out about a month ago that she began the process to have her entire adoption case disclosed. My mom, being the wonderful person she is, wanted me to be involved in the decision-making process and decide whether we checked the box "no contact" or checked the box "contact allowed, but through agency rep". After long discussion, we decided to check the latter, as we wanted her to be able to find her bmom and her half sister if she so desired. I am a social worker and professionally, I know how I should act and how I should support my mother; however, I have a wave of emotions going through my body, mind and soul and don't know what to do with them. Sometimes I'm angry, sad and happy. I've cried for the last 7 days since I found out. It's very hard to adjust to the idea that you are not the only child and you may not have the only grandchild. My mom was in college and the boyfriend was not a nice person, hence, had nothing to do with her after she found out she was pregnant. My grandparents had to send my mom out-of-state to some kind of home for girls to await the birth of the child. After she was born and all parental rights were terminated, my mom and my grandparents never mentioned it again. Years and years went by, with no word from the child she gave up for adoption. The woman is now 44 and just started the search. My mom stressed to me, as we are Catholic, that she never though about abortion and that she only wanted the child to go to a loving family who could give her the life that my mom was not able to give her. If anyone is going through this or has any ideas, or personal stories, I would love to hear about them. Also, I haven't seen any books about this and would love to read them if they are out there. Thanks for your support! "Shocked"