Thanks for your query.Based on the facts that you have posted it appears that your 15 years old daughter has problem of eneuresis once in a while.
Normally control over nocturnal urination is fully developed by the age of 8-9 years in females.
However this gets delayed in some girls .Do not worry it will get resolved as she grows up
As it is a sporadic issue she does not need any treatment.
She need proper counselling
and assurance from you.
Ask her to develop a habit of emptying bladder before going to bed.