My son who is five also has the same issue at night. He uses a "goodnight" pullup. About the bedwetting - I am very matter of fact about it and do not make a big deal about it. I do not compare him to other kids or make him feel ashamed. My sister also could not stay dry through the night until she was 7 or 8 years old, and my pediatrician has reassured us that many children cannot physically stay dry throughout the night.
However, since she previously was able to, I have to concur that you should have her checked for a urinary track infection. It does not have to burn, necessarily. My son had a UTI, and he said that it just felt like an urgency to go to the bathroom all the time. And he would go to the bathroom, but usually only a little bit of pee would come out.
As soon as he was treated everything went back to normal. In addition to the antibiotic, I also had him take cranberry supplements. Good luck!