Barbie Fairytopia: Mermaidia (2006) on Netflix

Plot summary

Elina, a flower fairy who has only recently gained her wings, is sought out by a young sea-butterfly fairy with word that her friend Nalu, the merprince, needs her. Laverna's Fungi seized him at the Crystal Cove. Laverna herself is confined to the Bog of the Hinterlands, and she wants the Immunity Berry, which would shield her from all magic and free her from her curse. Her henchmen, led by Fungus Maximus, push Nalu to say where the berry grows, threatening to pour a poison into the sea that would wipe out Mermaidia. Elina and Bibble set out for the cove, where they meet Nori, a mermaid and friend of Nalu who sees Elina as a rival.