Athena is a god who follows Odysseus in all of his adventures, advising and helping him in thousand different ways. In this particular situation, she wants to fuel Odysseus' anger even more, so she entices the suitors' worst traits and attitudes. She wants Odysseus to have his revenge, and doesn't want to risk him getting soft on the suitors. As a goddess of wisdom, she wants the order to be restored, and the offenders to be punished as they deserved.