ACT NOT RE-act
I am dealing with a almost 2.5 year old. Getting him to understand that him and I are on the same team, and that rules are there to help us all be safe and feel loved. It is very hard to not punish him for not obeying rules. One thing that I have implemented lately that is helping is acting, doing what I think is necessary at the time of conflict, but not over doing it with communication. It doesn't work for everyone, but it may help. Act with what is reasonable to you.
Ex; like if my son has an object he is hitting things or people with, and He throws a tantrum when I have to remove the object from him, it turns into a power struggle, or a conflict.
I may do a number of things that were suggested before, like distract him by being really goofy, or change the environment, finding acceptable alternatives i.e.: redirect his behavior like let him scribble on paper, or throw pillows, but at this point it may be to late for this.
I may remove Him from the environment and we may use the time for cuddling, and sharing feelings after he is calmed down.
I have found that it is sometimes useless and aggravating to us both for me to explain and lecture during the time of conflict unless we are both in the frame of mind for it. If I am not calm then it won't work. And if he is screaming and carrying on he is not going to listen. I am not saying not to communicate, just not lecture about the behavior until she can accept what you are saying. With a behavior that is really infuriating and pushing you to your limits like this, it is probably time for you to sit down and make some I statements. Write it down, and when it is the best time of day for her (like after a nap and a snack and while you are playing…) talk to her about how you feel.
Ex; I feel sad when you hit me and the Cat and Daddy. I want to be
treated softly. Tell her what is acceptable. Don't focus so much on what you don't want her to do as what you do want her to do. I would really like to trust you to be gentle and soft to mommy daddy and the cat. We really love you but hitting hurts. ….
This may seem to go far over her head. She will probably get most of it, and the intention of it. But it is mostly to train you. And you can also feel better that you have expressed yourself to her.
Sometimes children are trying to find out where they fit into the family, and of course they do this by testing out the boundaries. And sometimes when I give into my son by reacting too much to his ploy for attention it blows up at me. It is that theory that Dreikurs gives in his book Children the Challenge. An old book, but most of these books about parenting are based on his theories. Others just give practical application.
Your daughter may be getting a reaction out of you when a power struggle occurs that might make her feel like she has a place in the family, whether it is good or bad reaction.
I am sure that you are trying as hard as you can it sounds like it, and I may be writing this mostly for my own benefit so I can refocus on what I am trying to do. I hope this helps. And I have been opened up to a lot of new thoughts by all you wonderful mothers on this thread. Keep up on your Awesome intentions! 

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