I think your first course of action would be to bring this up with other members of your friend group and see how they feel. Have they also noticed this behaviour? Do they have any ideas how to deal with it? It will be easier to help this person if you work together. Just make sure you don't seem like you're ganging up on them. Maybe you can approach them with your concerns and then another friend can bring it up separately some time later. If you want to help always approach with kindness and love.
KbinItTogether