Neither Aleysia nor Medusa was skilled at the art of lying. They had been brought up to value truth and honesty above all else, so lying had never come easy to them.
Even after more than a thousand years of life, Medusa in particular found the idea of making up lies extremely uncomfortable. The Johnsons had always been good at lying, and she had never been very good at it herself.
As a former priestess of Athena, honesty had been ingrained in her. Now, forced into a situation where lying seemed necessary, she felt a deep sense of frustration, especially knowing Athena would never believe her lies. And just blindly accepting the lies then cursed her without even checking out the truth.