I would suggest few simple measures.. try them.. if didnt worked then see a doc ( Psychiatrist) --1. Avoid milk/coffee/ tea after 4 pm.
2. give sips of water before 2 hrs of sleep
3. make her go to toilet befoe sleep.
4. Get her awake at 80 min after she sleeps and make her to go toilet.( this is imp)
5 .Room Temp not to be too cold.
6. Dont Scold if she bed wets
7. GIve her praise and gifts for every dy nights ( plz be generous )
Tell her that you love her in every form.
Best of Luck!