How to deal with a bratty 16 year old?

I did a post a few days ago explaining my situation. My parents left me with my you ger sister and my neice. I'll link the question down below:

How to look after a 16byear old and 7 year old? ↗

So this is more of an update. I've not heard from my parents or my brother since they arrived a few days I go. I know there is hardly any phone service and the electricity is gone as well. I am just worried.

What they did do was not wrong. I am a guardian on their schools so that's great I guess, I forgot about that. So I took everyone's advice and they are doing after school clubs, staying round friends houses etc. However my sister came home at 2am last night. She told me "to f off and I am not mum and dad"

She is a brat. Mouthy and spoiled but very bright, and if she learns to not be mouthy she will be a very successful lawyer. There is 14 years difference between her and my brother. She is the baby of the family. My parents were not very hands on like they were with me, my older sister and my brother.

So what do I do here? I'm not letting her stay at her boyfriend's house. Nor staying out till like 3am regardless of it being a weekend. I think she has work tomorrow anyways. Omg how do parents deal with this? I think she is acting up because they are gone. And she knows that her older siblings don't buy the I'm a baby tactic.
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I hope I'm not repeating the same question. This is how to deal with my sister when she is mouthy, like I am not my parents. She was fine a few days ago, she's just gone all funny now
How to deal with a bratty 16 year old?
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