S.W.
Constipation can be a risk factor for nighttime enuresis (bed-wetting).
It also makes a difference that this is not primary enuresis (she has been dry for a long time, and is suddenly wetting the bed, as opposed to a child who has never been dry overnight).
Cosider Googling "Nighttime enuresis" for research. I found ots of info at www.bedwettingstore.com, the shopping site for Malem alarms. I don't think an alarm is what your daughter needs--sounds like something physiological is going on, if I were to guess-- but the info on that site helped me seperate reality from old wives' tales about bed wetting.
Good luck!