When will I get my first period?

I just turned 13 and k still haven't got my period. When do you think I will get it. I took many quizzes on it it said within a few months. Every time I see my older sister(does not live in the house) she asked if I got "best friend" or asked if I got my "monthly visitor" I always so no. She says that I will get it soon cuz she got hers @11 and my mom got hers @12 too. What do you guys think?

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