We have the same issue...
This is how that scenario has played out in my house & I am ok with it:
My oldest, now 5 1/2, Potty trained the day after his 3rd b-day & from that day on never wet the bed. He has always gone to bed with a cup of water. And drinks like there is no tomorrow.
My youngest, now 3 1/2, potty trained herself just before turning 2. She is dry most nights, but not consistently yet. I have tried taking the cup away, but dont feel right denying her hydration. After all, my son never had a problem.
My conclusion is, it is just her rate of development. So why fight it? She will out grow wetting the bed (eventually) if not, at age 5 I will teach her how to wash her own sheets. She is still in a night time pull up. I have tried taking the pull-up away. I got tired of doing laundry.
Helpful things:
I try to keep her well hydrated through out the day.
I try to be sure she is not over-tired when going to bed.
(These things seem to contribute to "wet" nights)
When she gets up in the middle of the night - for any reason she claims - I put her on the potty. She produces every time. When I dont she wets - every time.
So,
I have chosen not to worry about it. I dont want her to worry about it. Hope this was helpful!
P : )