When I was a little girl, my dr told my mum that my bladder had (either not grown to catch up, or was too big for my body, I can never remember which one) and because of that, I wet the bed every night. Apparently it's genetic because my aunt did aswell.
It's kinda embarrassing but I wet the bed and had to wear Nappies until I was like 13! It had slowed down by the time I hit 11 but I didn't completely stop until I was almost a teenager.
I'm not sayig this is your DD cause, but I'm sharing my experience so others can know that it may not 'go away' when parents want it too. The kid doesn't even know its happening and has no control over it. I know it's frustrating for the parents, but it can be frustrating for the child also, especially when they are older.
I do hope your DD grows out of it soon though, but in the meantime, re-assure her that wearing a nappy at night doesn't mean your a baby, it just means its easier to go back to sleep and there is no mess for anyone (including DD) to deal with.

I hope this helps. Good luck. Xxx