St. Jude's has done wonderful work with children with cancer..please follow this link and call them..
Our company has supported them for years as one of my former bosses had a child with cancer, since in remission. Good luck, I'll keep you and your family in my prayers.
If they need anything else, please let me know (I don't have a lot of money but I would be more than happy to donate some if they need to find a way to get your niece to another specialist! Please let me know if I can help!)