Sisters friend vaping

There is this guy who might be vaping. My sister is friends with him and idk what to do. He was in church and I saw a green light light up out of nowhere. He hid the “smoke” in his hoodie and looked back at my sister and waved. She said it was just a trending challenge but idk. I don’t want her to do it. But if she asks him he will know that I told on him. Advice please! (Sorry I have to post it in period talk but this one is really popular)

(UPDATE) I’m 12 and my sister and her friend are 14! You guys are telling me to “calm down” this very serious. Especially when he is doing it in church