Arabella is one of the granddaughters of King Triton and a niece of Ariel. She invited Ben, Mal, Evie, Jay, and Carlos to attend the annual Seaside Festival, a daylong celebration held among the Merfolks. She was at her grandfather's party when the storm appeared in Auradon.
- As a descendant of King Triton, Arabella could be a mermaid, or at least, a half-mermaid. It is then revealed that she does have a tail, but not all the time.
- She seems to be fond of the color lavender, a color that both Alana and Andrina shared. One of them could be Arabella's mother.
- She is also related to Ursula and Uma.
- She is described as a fashion maven and idolizes Evie's style, even having matching poison-heart necklaces and a similar v-braid hairstyle. She also wore an outfit Evie designed.