Being Home... ranting

I Hate being home from College. im 20 and my sister is too. she's never left home never done anything. i smoke because it relaxes me and helps with my anxiety. well since being home I can't Smoke till im 21. last night my sister and i was talking about how she was drinking and i was like yeah i don't drink that's why i smoke. idk why she felt the need to tell my mom (my mom already knows) and of course she started yelling at me again. I'm so annoyed. why do my sister's tell my mom everything?! You're 20 yrs old, stop fucking running to mom! legit Dionne with them.