Sara Wu

Sara appears in 2A where Luc helps her with a drone.

Sarah is voiced by Kelly Sheridan.

http://16hudson.com/characters.php says she is 10 years old, and the elder sister of Sam who is 7

they have a dog named Lucy

In I Heart Lucy she returns from shopping with Nye Nye to discover she's lost her cake

Lucky Sam mentions "Sam's Chinese New Year celebration takes a turn when his cousin loses an envelope." so Sam's cousin should also be Sara's cousin.

In Lili's New Year, Sam mentions to Lili that he once spilled grapejuice on his sister.