While not mentioned by name, in The Guardian's Challenge, it is revealed that Kiawe completed Olivia's grand trial and received a Z-Ring from her prior to the start of the Sun & Moon series.
She partially appeared in Young Kiawe Had a Farm! during a flashback, when Kiawe told Ash about how he received his Firium Z. She was mentioned in A Glaring Rivalry! when Gladion revealed that he obtained his Rockium Z from completing her grand trial.
She appeared in person in The Island Whisperer!, in which she traveled to Melemele Island and visited the Pokémon School, taking Ash and his classmates to visit Akala Island. She continued to appear during throughout Ash and his classmates' stay on the island, first in Treasure Hunt, Akala Style!, where she organized a class involving treasure hunting using Stoutland Search. During the treasure hunt, Lana found a Sparkling Stone, which Olivia took to be converted into a Z-Ring. The finished Z-Ring was returned to Lana in the next episode.
In Currying Favor and Flavor!, Olivia sent Ash and his classmates on a search for ingredients for the famous "Akala Curry". Ash was paired up with Mallow, with their search eventually leading them to Lush Jungle, where Ash was challenged by TotemLurantis. After Ash defeated Lurantis, Olivia showed up and revealed that the entire search had actually been a part of Ash's trial, and he now qualified to take on her grand trial.
In Trials and Determinations!, she battled against Ash in his Akala Island grand trial at the Ruins of Life, using Lycanroc and Probopass in a Double Battle against Rowlet and Rockruff. Despite their two opponents giving them a lot of trouble, Rowlet finally managed to defeat Probopass with Bloom Doom, only for Rockruff to impulsively attack and knock out Rowlet out of its desire to battle Lycanroc alone. Despite this setback, Rockruff was still able to defeat its evolved form, winning the battle for Ash. After the battle, Olivia gave Ash a Rockium Z and told him that Rockruff's behavior was a sign of it being ready to evolve soon.
She appears to be a very clumsy person, constantly getting knocked to the ground over simple tasks like walking up the stairs or opening a door. She also possesses the unique ability to communicate with Pokémon on a different level than most people, giving her a natural affinity even with highly guarded and aggressive Pokémon such as Kiawe's Turtonator and Ash's Litten.