What do I do

So for years I have been telling my parents to watch my little sister (she's 16 now). I said she acts weird hides her phone way too much, something is up. Well she's been buying vape online, using my moms credit card and the order is in my name and having it sent to the house. My mom confronts her and she said it's for a friend that she gave to. No I obviously don't but that at all. What I think is she bought it to take Snapchat pictures with since she thinks it looks "cool" (I'm not exaggerating this in the area where we are it's so common). Well we moved in the summer and she's at a new school and doesn't know many people. Well I honestly think she just wants to fit in and that's why is doing this. Here's the weird part I away trying to get into her email for my mom to figure out what really happened but couldn't so I tried to get into her Snapchat and shockingly I did (here's the thing though I'm super open my sister knows my passwords so she could easily do the same and I am worried about her) she has all her friends blocked from viewing her story except like 5 people I never heard her mention. Anyone have any ideas on this? I'm pissed at my sister for acting so stupid but especially using my name. I am pissed at these stupid vape companies because this should not be shipped to teenagers! Ugh sorry I needed to vent. Does anyone have advice for my mom to handle this?