Hi, dear I have gone through your question. I can understand your concern. First of all please tell me which type of blood cancer she had and what treatment she has taken. Relapse depends on type and treatment. To diagnose the relapse, you should go for complete blood count, peripheral smear examination and bone marrow examination. It will give you exact diagnosis. Then you should take treatment accordingly. Hope I have answered your question, if you have any doubts then contact me at bit.ly/Drsanghvihardik, I will be happy to answer you. Thanks for using health care magic. Wish you a very good health.