Estrogen is the hormone that is going to drive all of the body changes in your daughter as she goes through puberty. Estrogen is also a drug that has pretty profound effects on the brain. As estrogen makes an appearance in your daughter's body, it doesn't just show up and stay there, it comes and goes and vascillates. The brain effects will vascilate as well. This usually means that you will find your daughter has become a bit moody. She doesn't like her moods any more than you do. The very first thing that you can do, is acknowledge what's going on and help her come up with a system for dealing with the problem. So when she starts to feel the mood swings or you start to see the mood swings, identify it and give her an out. A timeout where she can go and resolve her angst. It can be two minutes, but it will stop an escalation. The reality is that some girls are more sensitive to estrogen than others. What that means is that some girls are going to seem a little more even keel, and some will seem a bit more emotional. You're going to have to figure out on how your daughter is behaving and what's going to work in your home. A hundred percent of the time, estrogen is going to be what makes girls a little bit moody. Anticipate it and figure out how you are going to handle it in your own home.