<human>: I found a receipt for vodka and confronted her. She literally posted something on Facebook two days ago about being 150 days so sober so I'm feeling pretty betrayed. I understand it's the illness of alcoholism but right now I am seeing red. I confronted her and at first she denied it and said when she bought the vodka she threw it away, but when I asked if I could breathalyze her she obviously freaked out. 

I haven't told my parents, and don't plan on it. They've gone through enough shit with her over the past year and it would ruin their vacation. Is it better for me not to tell them? She was for sure drinking and driving. I am not her parent but since I am the only one home am I crossing a line by taking away car privileges? She does not have a sponsor. She has lied and lied and is now trying to make me feel guilty that I'm not happy for her to want to be sober again. Our birthday is Thursday and now she is trying to play it up that she wants to spend the whole day with me, when really I can hardly stand to be in the same room as her. I would never be able to live with myself if she crashed the car and killed someone and then I had to tell my parents I knew she was drinking.

Can you condense the text into a few key points?
<bot>: twin sister started drinking again and my parents are out of the country. Do I have a right to act as parent in any way?