My wife and I just adopted a three year old girl and her younger sister. The three year old is potty trained. We were having problems with the three year old going to bed in her room. She would refuse to stay in her room at night and would have severe temper tantrums. Confining her to her room during her temper tantrums (while we ignored her) taught her quickly to stay in her room at night. However, she then started peeing and pooing on herself at night to get us to come and clean her up. We then started putting a change of clothes and baby wipes on her dresser every night and told her that if she pees or poos on herself, she needs to clean herself and change her clothes. If she came out of her room to get our help, we could confine her to her room. For a couple of weeks, she was cleaning and dressing herself every night and when she would tell us about it in the morning, we would acknowledge it and then change the subject. She now stays in her room all night and does not pee or poo on herself.
In the last couple of months, we have learned that three year olds will do almost anything to get attention. So we basically ignore the behaviors that we don't like. Maybe you can tell your daughter that if she has an accident, she has to clean herself and redress herself. If at first she refuses, put her in her room and don't let her out until she cleans and dresses herself. Then when she wets herself, she can take care of herself and you don't make a big deal of it. If she talks about her wetting herself, acknowledge her, but don't lecture her or dwell on the subject. This methodology may sound harsh, but it has worked great with our daughter. Good luck!