In Greek mythology, Callirrhoe (Ancient Greek Καλλιρρόη, "beautifully flowing") is the naiad daughter of the river-god Achelous who becomes Alcmaeon's second wife after his purification. She demands the necklace and robe of Harmonia, precipitating Alcmaeon's death at Psophis and the vengeance of their sons Amphoterus and Acarnan. Distinct from Callirrhoe the Oceanid mother of Geryon and from Callirrhoe daughter of Scamander at Troy.
Adapted from Wikipedia, "Callirhoe (mythology)" and "Alcmaeon (mythology)" · CC BY-SA 4.0
I.Second wife of Alcmaeon
Fleeing the Erinyes after killing Eriphyle, Alcmaeon is purified by Achelous, who gives him Callirrhoe and newly formed silt-land that did not exist when he was polluted. She covets Harmonia's necklace and robe, which Alcmaeon had left with Arsinoe (Alphesiboea) at Psophis, and refuses to live with him until she has them.
Alcmaeon returns under pretext of dedicating the heirlooms at Delphi; Phegeus' sons learn the truth, ambush, and kill him. Callirrhoe prays to Zeus that her infant sons Amphoterus and Acarnan grow at once; they avenge their father on Phegeus' house.
II.Homonyms
Wikipedia's Callirhoe (mythology) page lists many namesakes: Oceanid mother of Geryon, Scamander's daughter wife of Tros, Meander's daughter, the Coresus maiden, and others. The atlas id callirrhoe-achelon is only Achelous' daughter and Alcmaeon's second bride.