Is Gap Between Periods After Having Periods For The First Time Normal?

Hi. My daughter will turn 13 in May. She had a mensutruation period around three months back first for a day or two and again after a gap of 5-6 days for another 3 days after which it stopped. I assume this was a menarche for her. After that she has not had any flow till date. We have had a CBC also done last month and all is normal. She has a childhood illness hsitory. When she was eight years old, she was diagnosed with leukemia and underwent treatment like chemotherapy and radiation . But now she is absolutely fine and has been off all drugs for the last one and a half years. My query was that is this kind of gap normal considering the data i have provided.Pls advise