Yet another period question......................…

how can i get my mom to talk to me about periods? the only information i can ever get is from here, other websites, or -ed cles at school, and the majority of it says that puberty is hereditary, i tried bringing something up when i was in fifth grade, (im in seventh now) but she didnt seem to want to talk about it. i tried getting her to show her a website on the computer about a month ago, but she didnt seem to like that either, i dont know what else to do, i dont just want to bring it up because the only time i ever really have a chance my dads there or shes 'busy' watching tv. i dont know how to talk to her about any of it... how can i get her to talk to me about periods and stuff before i get it?