First and foremost, don't make a big deal out of this because it may be caused by anxiety, and will certainly cause it if your little one feels she is being a nuicance / dirty / childish, and so on. Have a gentle word with her during the day time, don;t mention the bed-wetting, and have a quick word with her teacher as well.
Practically, try not to let your daughter drink anything after about six in the evening, just a small cupfull of milk or what ever at bed time. Set your clock for about midnight, and wake her gently and take her for a wee, and pop her back. Eventually her brain will learn to recognise the 'bladder full' signal and wake her up so she can go to the loo herself.
Lastly, make sure she is getting enough sleep - if she is too deeply asleep to pick up the 'bladder full' message, she will simply sleep through and wet the bed.
Remember, all children grow out of this, so be patient.