Hi Everyone.I am engaged to the nicest person i've ever met and ...

Hi Everyone.I am engaged to the nicest person i've ever met and when we got engaged we decided that she should go on the ( YASMIN ) pill to prevent any sercumstances.she skipped it for a month because of financial constraints and now she got back on it put the only problem we both have is that hasn't menstrated in atleast 4 weeks now. Is this one of the side effects and will she eventualy menstrate?. as I understand and heard from some people this intends to happen to some people. is this TRUE ?