Hi there, my 7 year old non-D son wore pullups till he was 6. He just was a deep sleeper, but I always tested him anyway to see if he had high BG and never was it above 100. My 5-year-old son who has T1D stopped wearing pullups at 4 1/2 and only ever has bedwetting incidents if he's really, really high and drinks a lot of water during the night as a consequence. Fortunately, he's a light sleeper and has trained himself to waken and go to the bathroom... which is almost always a signal to me to test his BG and give a correction.
To a certain extent, the child's ability to control their bladder through the night is genetic — my pediatrician said that, knowing my son's father wet the bed till he was 6 was a pretty good indication that my kids would likely do so as well. But that doesn't mean you can't coach them a little toward learning control. What I did with my older son was, I made sure he went to the bathroom right before climbing into bed each night, and did not allow him any water at his bedside. I also gave him incentives toward wanting to have underwear instead of pull-ups — like saying, "if you can go 3 nights in a row without wetting, you can wear big-boy undies instead of a pullup." and then, the rule was, if he continued staying dry, he could keep the undies, and if not he went back to pullups until he managed 3 days in a row. Also, I had a plastic mattress-protector on the bed under the sheet, and I told him that once I was sure he wasn't going to wet anymore, we'd remove the protector (and I did that with great fanfare when he'd been without wetting for several months).
So my guess is that in your CWD's case, it's probably a bit of both — deep sleeping + the D makes her more prone to it. You can try the "training" techniques I used and see if that helps a bit, and of course we're always after better BGs at night... maybe to a basal check to see if perhaps her basal insulin is too low to prevent nighttime highs? But beyond that, I wouldn't worry about it too much. She'll likely grow out of it.