Help needed! how 2 get.....

Hiya,
Any suggestions on getting a just turned 4 yr old dry through the night?
She has had problems with toileting, tk a yr 2 train properly n is under hospital 4 severe constipation that she takes medication 4.
She is very good in the day now.
Have stopped givin juice after 6pm. she goes 2 bed at 7/ 8pm, sleeps through til 7/ 8am.
She is a heavy sleeper 2, n this may b the problem. We keep the bathroom lite on all nite so if she does wake she can go. She is still very wet of a morning n is in no rush not 2 wear em!!!
I am tryin 2 encourage her but dont want a battle, especially with the constipation and the arrival of baby no.2 still bein relatively new.
Hubby not concerned but just hear so many horror stories of kids who grow 2 b teens n still wetting.
Should I try wakin her when we go 2 bed 2 c if that helps?! Havent done this yet as she is such a good n heavy sleeper that I havent wanted 2 break her very good slep pattern.
Very frustrating n confused, mummyand2. xx
any advice welcomed!!!