My son is 5 now. When he was 4, he drove me nuts trying to help him get dressed. He wanted to get dressed by himself, but he wanted me to watch him and help him if he couldn't quite get it himself. That's all normal, but he took forever when he got dressed because he would jump around and chatter the whole time. I told him to focus and concentrate so many times I had dreams of me telling him to focus and concentrate.
So one day, I told him. "I know you want to get dressed by yourself. You are a big boy now. I believe you can do it all by yourself. Do you think that you can try to do it all by yourself? I'll be in the bathroom washing my face. If you have any trouble getting dressed, come get me." I went to wash my face. Suddenly, it was very quiet. But I waited it out, and before I had finished, my son came bouncing into the bathroom with a huge smile on his face. "I did it! " He beamed. Then I noticed he had his pants on backwards. I smiled down at him, and told him he did a great job with his shirt, but to take a look in the hallway mirror. He came back. "My pants look funny." We laughed, and I told him to carefully take off his pants, look for the tag, make sure the tag was next to his tummy when he held up his pants, and to try putting them on again. He came back a minute later and said thank you to me. After that day, I leave him alone to get dressed. I sometimes have to remind him to check the mirror, and help him turn his clothes the correct way when he misses the first time, but he picks his own clothes, gets dressed on his own, and I no longer have to deal with telling him to stop bouncing around when we do things. If your daughter gets distracted by other things when you leave her alone to get dressed, try making a game of it. "Let's see what we can do in 5 minutes. Will mom win, or will you win?"
As for fixing your daughter's hair, if she doesn't comply with you telling her to be still, she doesn't get her hair done the way she wants it. Simply brush it, or do what you can quickly. If it truly matters to her, she will be still.
My son loves to talk. We practice quiet time during the day. We do a kids yoga DVD every day for 30 minutes. (Yoga Kids Fun Collection with Marsha Wenig) The yoga has brought peace into my life. I also use the yoga to curb any arguments or temper tantrums. We also have independent time where I have my son draw, color, read his books and magazines, or do puzzles quietly for about 30 minutes every day. I put one of those 30 minute blocks in the morning and one in the afternoon. It helps to keep my head from exploding every day. I need my quiet time. And the kids yoga is fun to do together.
Since my son loves to talk, I try to make sure I give him my undivided attention at least once in the morning, once in the afternoon, and during our bedtime routine. We do a storytime daily. I ask him questions about the books we read. He also loves to tell stories. So we started doing story building recently. One of us starts the story, then we take turns making the story together, until one of us finishes that story. We also talk a lot about his artwork. He loves to ask me what I did when I was his age. We love going on discovery walks and talking about things we find or see happen. Look for ways to channel that love to talk.
As for the question asking, I would explain once why I said no. Then when she asks again, keep it short. "I told you that we don't have money for that now. We must do something else now. etc.) Don't ignore her, but keep it short. If she starts to nag you with the same question continuosly, disengage the conversation. "I said no." And then you walk away.
Hope that helps you both to have a more peaceful time.