Most writers credit Athena with laying a curse on Medusa. However, it could also be the case that Athena was not trying to curse Medusa but instead help her. Athena is a virgin goddess, one who was the patron of Medusa. When Poseidon raped Medusa, she called out to Athena for both forgiveness and guidance. Here is where interpretations differ. Athena's decision to curse Medusa with her petrifying stare would not make sense if Medusa was the victim of rape. Thus, transforming Medusa was not an act of rage, rather, it was an act of protection.  Athena could not punish Poseidon for what he did to Medusa. As a result, the goddess did the only thing she could do, which was to protect her former priestess. Giving Medusa the ability to turn people to stone then becomes a mechanism of self-defense than it does anything else.  It grants Medusa the power never to feel helpless again when faced with similar situations.
While it would seem much more rational that Athena was blessing rather than cursing Medusa, it is also possible that Athena cursed Medusa out of jealousy. Even though Medusa sought Athena's counsel, there is still a case for Athena being angry towards Medusa. One of the things that could have fed this anger was jealousy. Medusa originally promised herself to Athena, but her promise to Athena came undone when Poseidon raped her. One of the staples of being an Olympian god's mate was that once claimed, they were bound to be mates forever.  Athena could have arguably felt betrayed by Medusa since Poseidon claimed her, even though Medusa promised herself to Athena. In turn, the virgin goddess would feel inclined to lash out in anger against Medusa for this development.
Rejecting the premises