I don’t begrudge a coworker befriending a supervisor. Maybe they are genuinely friends.
As much as you like people who come in a do their job and go home. Many others like it when they come in and a friend is there and they can chat, have a good time, and still get their responsibilities done.
If they can’t get their work done, then it’s a supervisors issue. You don’t have to do their workload.