I think she should probably get the killed vaccine (the injection, not the nasal spray). Check with her doctor, of course. But god forbid her leukemia reoccurs, I think it would be important for her to be protected.
I have talked to several medical personnel recently about the H1N1 vaccine. All have recommended that a child who has a medical condition should be the first to discuss with their physician if they are a candidate for the H1N1 vaccine. Most children will be advised to receive the vaccine if in their early twenties and younger. However, there may be a small population of children who would not be able to receive this vaccination. Please talk to your child's physician and oncologist, if need be.