Are you (she) experiencing this right now? I.e. no menstrual cycle or any other sides? Or just involved in the "trying to get pregnant" phase? You'd probably be told to give 3 months between ending BC & starting trying to get pregnant - I guess maybe a general safety window for the BC to "clear her system". After that, assuming everything works right, I guess its just time. If there is an issue, the OB/GYN should be able to measure "fertility" or something like that.