Do you think I'm being to hard on my younger sister about her pathetic fake friends or is she being a brat?

My little sister won’t speak to me because I roasted her new “friends” and I’m just jealous. No I’m reacting sarcastically and snarky because my sister’s friends are a bad influence in her and she won’t listen. Mom was too busy to notice so I’m going to have to break the truth if her. I’m trying to get her to understand that those losers aren’t good influences and to stop hanging out with them. She told me off why am I acting this way and I’ve been a teenager. I told her that yes that’s true but I lived longer than her and besides she is home safe and it doesn’t really matter now. I don’t understand why she won’t listen. She told me earlier, “You know sometimes you can be a real bitch.” And I told her off, “And you’re being a stuck up brat that thinks she knows everything. I’m telling you, DO NOT HANG OUT WITH THOSE BUM LOSERS THAT WILL MAKE YOU LIFE HELL! If you do I will tell mom that you’re going joyriding this weekend. You better listen to me before before dumb, dummer and dumbest ends up getting you killed.”
Yes it was harsh but she needed to hear the truth. I’m not going to be nice and let her get hurt and protect her feelings. She told me to stay out her life and she wish I wasn’t her sister.
Ouch. I told her fine but don’t come crying to me when I warned you! Yes I am a bitch because I care about her and I don’t want her around those losers! She’s 15 and I’m 26.

Do you think I'm being to hard on my younger sister about her pathetic fake friends or is she being a brat?
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