A.S.
Hi, E.,
My heart goes out to you! I was in the same place as you were a few months ago, so I bought the book Positive Discipline for Preschooler and Playful Parenting (a really good one!).
The best thing to do is to treat her positively and she will hopefully reward you with good behavior. I found both books to be REALLY effective and now I am no longer yelling. Basically, kids are GOOD. if they are misbehaving, it could be that she wants your attention. In that case, instead of giving her negative attention, just start playing with her. If I want my son to come brush his teeth, he usually hides from me. I COULD start yelling and counting and trying to pull a power play over him, but all he really wants is to play. So I start to look for him and then I find him and tickle him and then carry him to brush his teeth. By this time he is giggling and having fun and we have no issues. Granted, it sounds like a lot of work, but it is probably less work than what you are going through right now. If there is something you can remove her from, then just remove her instead of arguing about the fact that she should stop doing something. If my son is banging his cup on the table and refuses to listen to me when I tell him to stop, I simply take it away quietly and don't say anything about it to him. If my 3 year old starts saying "poopyhead!" he just wants to play (I got this from Playful Parenting), so instead of reprimanding him, I say, "call me whatever you want, but DON'T call me snickerdoodles (or some other nonsense word)" and sure enough, he will call me snickerdoodles and then we go from there and play. It is all about playing and getting attention. The more negative attention you give your daughter, the worse she is probably going to misbehave, because she is not feeling good about herself. If kids don't feel good about themselves, they have a tendency to keep acting negatively. Don't reprimand her in public or in front of her friends (or yours). She will be embarrassed and maybe act out again in order to cover up her embarrassment. All of these issues were covered in the two books that I read. I also read Between Parent and Child and that is a good book, too.
Give your daughter some lead time if you want her to do something. For instance, if it is bath time, you may want to give her a warning that in five minutes, she will have to take a bath. That way, she can finish up what she is doing and be ready in five minutes. Often, parents expect kids to do things as soon as you order them to (My husband is like this), but the truth is, no one likes to be demanded to do something ASAP. Think about how you would feel if someone interrupted your work to do something RIGHT NOW. So, I started using a timer and told my 3 year old son that I was setting this for five minutes and that when it went off, the TV was going off (or whatever activity he was doing). As soon as it did beep, he was totally ready to do what I had asked him to without a fight! It is so amazing. So please be patient with your daughter. Give her lots of love. If she has a tantrum, just hug and hold her. Maybe don't put her in time out, but go and sit with her in a "cool off" period. THat way, both of you can cool off and then you can discuss without yelling.
good luck!