I'd personally encourage her to give it a try without a nappy. One thing I bought for my oldest DD was a mattress protector that goes across the bed on top of the bottom sheet and has flaps that tucks under the mattress. It's made from mainly material, so is less noisy than the regular plastic underlays that cover the whole mattress.

I think it will probably be a trial and error thing for you. Having been a long-term bedwetter myself, and having one DD who has been, I know all the tricks of the trade, and as I'm sure you know, it's more likely that she'll just grow out of it. I think showing confidence in her by letting her try to sleep without a nappy might help, if not, maybe getting her up to go to the toilet before you go to bed would be helpful.

Good luck.