[Rivière]

I'm glad to hear your sister has come to listen to reason! That said, I don't think it would be a bad idea to keep an eye on her for the time being. Promises and agreements made with words are one part of the deal. Her actions need to show it as well. See how she is for the next month or two and go from there.

And by keeping an eye on her I don't mean constantly bothering her. Just keep an eye out for any changes in behaviour, alcohol missing when you're not around, or bottles subtly being replaced with new ones. It's not intended that you distrust her words, but as her sister, you're showing that you love and care for her by being observant of any concerning behaviour.