Without knowing her age I can only say that it sounds to me as though she is simply a very sound sleeper. If she is sleeping through the alarm she is most certainly sleeping through the feeling of a full bladder. If this is the case she may continue to do this until either her sleep patterns change or until she reaches an age where she is able to hold it all night without need to go. To be certain though I would first rule out physical reasons such as neurological problems or problems with bladder control (weakness, valves, congenital probs). Bedwetting is not even technically considered a problem until a child is over the age of 7 or if it develops after a prolonged period of being consistently dry at night. Problems such as anxiety can also contribute to the problem.