Gabriella is a young mermaid who becomes a close friend of Ariel. She appears to live outside of Atlantica, but sometimes comes to visit. Like Ariel, she is curious and inquisitive, with an adventurous spirit. She shares a close friendship with Ollie, who serves as her interpreter, as Gabriella is deaf and communicates exclusively through American Sign Language (ASL), however she can also lip-read.
Gabriella first appeared in the episode "Wish Upon a Starfish", where she meets Ariel after seeing Ariel express her desire to dance. Gabriella expresses a desire to be able to sing, and convinces Ariel to come with her to seek out the magical Wishing Starfish. The two girls find the Starfish after facing many dangers together, but he is revealed to be a fraud. The girls are saddened, but Ariel reminds Gabriella that she expresses herself beautifully through her sign language.
Gabriella would reappear in the episode "Ariel's Treasures". Gabriella returns to visit Ariel and is introduced to Ariel's extensive collection of human objects. However, Ursula, as part of a plot, casts a spell over the collection, causing each item to attack other fish and merpeople. The two girls are able to stop the spell, but only by destroying each object.