I know an adult that has this problem and her remedy was using a mouth guard.  The same as what you would use in a game of sport.

my son also grinds his teeth, but not all the time I find that if he is having a bad dream he will grind his teeth and talk in his sleep. i do not wake him but answer to him softly that I am here and everything is alright. I also rub his back for a few minutes, and this seems to sooth him and soon he is once again sleeping peacefully with no talking or grinding. If your daughters grinding is as loud as my sons then it must wake you. I do not know if this will work for you but it has for me and anything is worth a try! My ears are sore just thinking about it. Good luck from someone who's been there.