Hi. I wrote a research paper on bed wetting in college, and this question is asked so frequently that I typed up a standard response to it. Adjust the instructions for gender.
1. She should increase the amount of water (not juice or milk or soda) she drinks before 3:00, maybe 2 extra glasses. This will give more opportunities to do steps 2 and 3.
2. When she needs to go pee, she should wait a few minutes before going to the toilet. She may be able to wait only 2 minutes in the beginning. She should be able to work up to 15 minutes. Don't have her wait longer than that, however, because it can lead to bladder infections. This will both stretch out the bladder so that it can hold more and strengthen the sphincter muscles holding in the pee.
3. Teach her kegels. The easiest way is to teach her how to stop the flow of pee. You can demonstrate if you like. Again, this will strengthen the muscles. It is important to do this at the begining of the flow and to push the pee out at the end to avoid bladder infections.
Doing these 3 things sometimes eliminates bed wetting entirely, and sometimes reduces it. If that doesn't work, using a wetness alarm is the most effective way to stop bed wetting. Don't use it until a child is at least 6.