How did they become sirens

One day Peisinoe, Aglaope, and Thelxiepeia decided to sing in the water, but little did they know that Persephone was being abducted by Hatties. Persephone's mother (Demeter) was furious and angry, that her daughter went missing.

Demeter decided to blame it on Peisinoe, Aglaope, and Thelxiepeia. Because they were her protectors. Demeter cursed them with the tail of the mermaid in water and the body of a bird on land. J