Should I tell her ?!

Okay so I'm 13 and I started my period the day before new years <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">eve</a> ( 3 days after my b-day). Its now June and I still haven't told my mom 🤐. The reason I didn't tell her is because she tells too much , she's the type of mom who would post it on Facebook or something 😂. The only person I've told was my step sister and two of my cousins . Should I tell my mom ,any advice on how I should tell her or how to explain why I waited so long?