Explosive anger

I don't know if this thread even belongs here, as I don't feel it's an attachment problem. But my 7-year-old daughter has been having the most terrible outbursts of anger lately. And beneath that anger lies a deepfelt frustration at knowing that she was abandoned by her birth mother (in China) when she was just two weeks old. "How could she do it?" she keeps asking me. She directs her frustration and anger at me, which I can understand: Her birth mother is not here. I am. How do I help her? Has anyone else gone through this with their child?