You shouldn't talk behind people's backs.
Sarah think the new employee, Fred, does not do his work fast enough.
Sarah wants to do something about the situation.
Sarah decides to talk to Fred and see if she can help him get faster at his work.
Sarah complains to her coworkers that Fred is too slow and that she will tell the boss.
Fred tells Sarah he appreciates the offer, he realizes he's not that fast yet.
Sarah's coworkers tell her that she's not being fair to Fred since he's new.