Approximately 5-7% or so of children her age are enuretic at night. You really needn't do anything about it if you wish. The situation will eventually improve. There are interventions (prescription medication, wet/stop alarms) that can be employed, and you might want to talk this over with your daughter's pediatrician. Rememebr: the interventions are entirely optional; there is no compelling reason to intervene.
My son is 10 years old and has the same problem. We tried everything and nothing really worked until we went on medication. It seemes to be a hormone difficency that he will grow out of but in the meantime he was embarrassed at sleep overs and we had back up plans incase he had an accident. I don't know how long we will be on the meds, but in the meantime, it has helped him.