HI C.,
I am very sorry about your daughter's friend. That is a very traumatic event to happen to her so early in life. I thought there was a medication to help with the antidiuretic hormone, but perhaps you do not want her to be on medication which I completely understand.
Well, my dd is only 3 but she was waking constantly with nightmares and night terrors and it was taking over my life-literally, because neither of were getting any sleep. Thus, we would both be very cranky and unpleasant during the day. It was a vicious cycle.
Here is what helped me TREMENDOUSLY after seeking tons of advice. She now rarely ever wakes up unless I 'break' the rules.
1) absolutley NO liquids after 5 pm. (she goes to bed by 8 pm) I make sure she drinks tons of liquids all day so that she doesn't get thirsty at night. I constantly remind her to drink, drink and then warn her at about 430 that she won't be able to drink anymore soon.
2) I also make sure she doesn't eat dinner to late (for nightmares/tummy aches) Not sure if this would help your daughter but anything is worth a try isn't it? Some foods can also cause urination.
I would definately try waking her up BEFORE you think she has to urinate. You can set an alarm for yourself to wake her or set her up with an alarm in her own room (hopefully she hears it and wakes) this was something I tried with my daughter. Make her use the restroom even she doesn't feel like she has to go.
This is all I can think of for now. But the no liquids has to work eventually because she won't have mush in her bladder throughout the night if she completely empties by the time she falls asleep.
Good luck. My poor brother used to wet his bed all the time and would tell me that he was dreaming that he had waken up, walked to the bathroom and was using the toilet. Next thing he knew he was actually waking up and was in bed all wet.