It is ...

Impossible

Our goddess is good to us men. She could never have acted like this out of pure selfishness.

This is unfortunately the truth. A hidden truth. Our goddess has done much worse to Arachne. But she is a goddess, we cannot pretend to understand her decisions.

Anyway goddess Demeter, why reveal this to us? Since you say you adore your niece. That we pity Medusa?