@Seiisaysyo if your looking out for a friend it's not possessive it's protective and sometimes that can be a bad thing. But this is not one of those times if you genuinely think that this person is a bad influence on your friend then you need lay your point down hard and give an honest and direct statement on how you feel about the situation and have solid argument on how they are a bad influence. So that you can illustrate the problem at hand. Beware sometimes it can become an argument but if you really care about your friend than you can just be there. To support and look after them
I like to read and follow the dopamine that's all.