Lisa I am not sure if Prednisone has the same mineralcorticoid properties as hydrocortisone (I know dex does not).  Has your daughter had the PRA level tested (plasma renin activity) since starting on the pred? You could try and increase her salt intake. Is this happening at night only?  I know this isn’t easy and really an upsetting problem. I would contact your endo as it seems odd this should have happened since the pred!  Good luck and please keep us posted.