Sorry to hear your little girl's brave fight with cancer! I am a parent myself, so my heart and my paryer go to her...
You may have been aware of a cancer treatment, Gearson therapy. YOu can get a book on Amazon with the same name. They advocate plant-based diet to remove cancer-friend environment inside of our body to make them deminish eventually. I m no expert on this topic at all, so do your own research to see if the information is beneficial...
Stay strong!