From Bulbapedia, the community-driven Pokémon encyclopedia.
Siara is a Mission Guide from Pokémon Learning League. She assists students when they watch Science lessons.
The Learning League Lab’s Science Specialist, Siara is often seen performing another experiment, sometimes with explosive results. She's crafty and clever and is willing to show how things work and is able to create things on hand.
Just like other women, Brock is often seen trying to flirt with her, and just like other women she's either flattered or brushes it off.
It is revealed in the episode "Giving Back" that she volunteers her time building homes for a habitat for humanity-type organization.