told my family about reunion - it didn't go well

The good news: I am in reunion with my birth mother's family. (She herself passed away before I found her, but I'm now in touch with her sister, mother, and 3 daughters, and they've welcomed me as a long-lost family member.) The bad news: my (adoptive) family isn't entirely supportive. In fact, it's breaking us apart. My father actually is wholly supportive - he's never been one to feel insecure or worry much. He's happy that I've found nice people and wishes me well. He's curious, asks questions, is genuinely happy on my behalf... that part's great. My mother, on the other hand, is... well, she's unhappy and uncomfortable, but at least she's trying. We've battled about my desire to find my birth parents for decades (I'm in my 30's and have ALWAYS known I wanted to search - she has always been adamantly against it). I knew she would be unhappy - she's always come straight out and said that she felt threatened and unloved, like I was looking to replace her as my mom whenever the topic came up. No matter how many times I told her it was about adding to my life, never about subtracting from it. I honestly think that the only reason she didn't flip out upon hearing was that I started by explaining that my birth mother was already gone. I've never understood her take on it, but I respected it, and allowed it to hold me back from searching for a long time. She has told me that she'll try to be happy for me. Best I could have hoped for, really. And now, the downright ugly. My sister is also adopted (not biologically related to me), but has never been curious about her own biological family. After telling my parents about my search and its results, I called her to let her know as well, figuring she'd be largely uninterested in what I had to say, but also figuring that being honest and upfront was the right thing to do. I barely sketched out my discoveries before she opened fire on me with the nastiest insults she could think of. In short, she told me that I've never been a true part of our family and I should go hang out with my "real" biological family because they didn't hate me... yet. (Honestly, yes, I have struggled over the years with my relationships with my family, but I do love them and I make sure to express it in my words and my actions. I dote on my niece and nephew, her two kids, and I encourage my small son to be close with his cousins. I am the go-to person in my family whenever someone else needs help; I previously left my career as a teacher to become a caretaker for my mother when she was struggling with a series of health problems. I set my sister up with a friend of mine because I thought they'd be a good match... and he's now her husband. I'm not perfect and my path with my family hasn't always been smooth, but what she spat at me was truly awful, purposely hurtful, and patently untrue.) The hate and spite that poured from her for about 15 minutes totally shocked me. She asked me how I thought she'd respond, and I said, "Well, I was hoping for a little support from my 'real' sister." She said she had none for me and hung up. It's probably obvious that we aren't speaking now. My parents are torn up about the rift. I am too. I cannot even fathom how my news (delivered calmly and carefully in clinical language - "I discovered that I have a biological aunt and biological half-sisters, and I'm now in touch with them - they've welcomed me with open arms") could lead to the sort of venom that my sister spat at me. I should probably add that my sister saw her best friend, a fellow adoptee, through her own search and contact/reunion with her own birth mother, and supported her 100% through the process. I know that nobody here can give me the clarity I seek, the insight into my sister's mind and thoughts. But I'd love some feedback from people who have spoken to family about their reunions - the good and the bad. Perhaps in hearing others' experiences, I'll find a thread that leads me to understanding my sister's meltdown. And perhaps see a way to bridge the distance she's now thrown between us... Thanks.