K.M.
My daughter began emotional outbursts like that when she was closer to 4. We very quickly discovered that there was usually an event that triggered the insecure emotions, the first being her dad and I divorcing. From there, it could be an event at school involving her teacher or friends or something that her dad or I said. What we finally figured out was it wasn't the event that mattered as much as *her perception* of the event. She began acting out in ways that were unacceptable, like stealing, and we eventually got a child psychologist when she was about 8. He helped her to sort out some of her feelings and put things in perspective, but it definitely didn't cure her long term. The biggest benefit of the psychologist was that she got to vent confidentially to someone that wasn't her parents.
Long term, we've had to talk to her before it escalated into blaming us. One thing we learned was to stop her and ask her if her behavior is appropriate, have her explain why it is or isn't, then ask her how she could have handled the situation better. We've had days where that exercise was done 3 times in less than 10 minutes, but over time, it's been a valuable tool for us. As she matured, we were able to discuss her perception of the situation and then ask her what other possibilities could be. It really allowed her to think past the emotions and look at the whole picture. She wasn't always able to come up with other scenarios herself and we would help walk her through that, but she is 12 years old now and is much more thoughtful and rational than she was before.
Definitely make sure that she isn't having any issues as school, like bullying or teasing. Remember that most of what she's going to get upset about doesn't have *anything* to do with your love for her. It's because she knows you love her that she acts out that way. Good luck and let me know if you need any other suggestions! I've got 8 years worth of hits and misses with that girl!